For those who want to test their SD card (normal, mini or micro), here is a very detailed post on Ebay.
I'll paste it here also in case it disappears from Ebay.
nupshutup says:
"Testing for fakes : SD cards, USB drives, MMC, CF and other portable or removable storage devices
As many people have reported there are a very large number of fake and counterfeit SD cards on Ebay at the moment. The reason for this is the large profits which sellers can make and the minimal import cost associated with such a high value item. Having spent quite some time contacting manufactures of SD memory cards in the course of my job I have been shocked to find that the vast majority are not only selling fake items but are very open about it.
To give you an idea of what kind of scale the problem is I contacted 45 manufacturers and wholesalers of SD cards throughout South East Asia :of these only 1 was able to provide me with proof that they held the correct Patent and Licensing for the production of SD cards. During this research I found numerous suppliers who got very upset when I suggested that selling counterfeit items was in any way wrong :the standard response was "We supply many people in Europe and US and there is no problem :they are making lots of money and are very happy" (quote lifted from an actual email).
Before you buy a card use you head:
1. While the physical appearance of the item is a good indicator the fakes are getting better and better. Remember that the act of printing a sticker is very simple and the casings are a dime a dozen. Look out for anything out of place such as misaligned stickers or serial numbers which have been badly printed.
2. If you are going to order a card don't trust a webmail Email contact address.
3. If you are going to order numerous cards order a very small sample first and refuse to pay a premium :often you will pay a lot for samples and receive "real" products then get shafted on the actual order.
4. If they are selling a large quantity and are in Australia ensure they have an ABN. If they tell you they are going to charge a premium for supplying a tax invoice consider that an insurance policy and just swallow it (or withhold 50% of the purchase price and send it to the ATO :as you are legally entitled to do).
5. If they have less than a 100% positive feedback rating then forget it :furthermore if they have never sold an SD or memory product before and instead have sold numerous very low value items in a short period of time consider them to be a High Risk (people do this to get their feedback rating up before cashing in).
6. Don't buy if they don't have a return policy. If you decide to risk it only pay what you are willing to lose ($12 for a 4 GB SD card is too good to be true but if you want to risk it remember you might get a 128mb card which isn't such a bargain).
7. Avoid sellers who charge high postage and handling costs :this spells disaster for you if you try to get it replaced because they will charge you the same amount again (the scam runs along the lines of : you buy an item for $3 pay $10 postage, it doesn't work so you send it back and pay another $10 to get it back to you :it still doesn't work so you ask for a refund, the seller happily refunds you money after you send the product back and they makes a tidy $20 and still has the product to sell to some other sucker).
8. If you must buy from someone who is profiting of high postage costs consider offering them more for the product in return for a reduced postage cost :this will save you if you have to send the product back and pay postage a second time.
9. Do your homework :recently 64, 128 and 256 mb Sandisk SD cards have flooded the market so the price is genuinely low (wholesalers getting rid of stock) but 1 GB and above cards are still not dirt cheap. Consider using an online price checker service such as StaticIce to find out what the going rate for the product is and then deduct a reasonable amount for retailer markup (5 :25% is a good guestimate). If you can't work out why a product is so cheap then it is probably fake :check Alibaba.com for suppliers of the product and email one for a price list (I don't think I am allowed to name names of known counterfeiters but lets just say that if the supplier has a hotmail address or other web based email address ... you fill in the blanks).
10. Once you have the product test it properly the first day you get it. If you buy a 2 GB SD card and it takes you 3 months to take 1 GB of photos there is a good chance the seller will either be long gone or ignore you when you complain.
Testing:
Most of these instructions apply to SD cards but can be used for other memory cards and USB drives as well.
1. If the card has a write prevention switch (as all SD cards do) put it in the Read only position and try to write to the card (if you can then it is a fake).
2. Reformat the card in you camera (if the card has an overstated capacity this will either fail or format the card with the actual amount of available space).
3. Copy a series of files to the card. Remember that most SD cards are formatted with a FAT file structure so files over 2GB can't be saved to them anyway. Try a series of 100mb files (recorded audio from Windows Sound Recorder found in the Accessories menu will do the trick, just record silence for ten minutes (no microphone needed)).
4. Copy a series of small files to the card :try text files or your temporary internet files. Do this until the card is full. (Testing capacity and the Master File Table).
5. If it is an SD card or similar put it in you camera and use the Video Record function :record for 30 minutes (or as long as you can) then wait for the camera to save the file. If the camera can't save the file and tells you the card is invalid then again you have a dud on your hands)
6. Attempt to open a large file directly from the card :a Photoshop file or even one of the silent audio files you recorded earlier will do the trick. You can usually connect you camera to you computer in Mass Storage mode to test this.
7. Use a program such as SiSoftware Sandra Lite (Free) to test the read and write speeds of the card. This software has built in benchmarks so you can compare the results to what you should be getting. This requires either a card reader or you camera to be connected in Mass Storage Mode.
8. Use KillDisk to view the contents of the card. Run the disk wipe on the SD card (which may fail with fake capacity cards) then view the contents again. When you scroll through the sectors move towards the end and look for changes that are out of place (the first 100 or so entries are the MFT and will be full of gibberish, then it should be all zeros :if it is 99 instead of 00 you have a card with overstated capacity).
9. Finally before you complain to the seller check that you camera can actually read the card :by this I mean many cameras can not handle cards with a capacity of over 512mb, just because you found someone on the internet whose camera could doesn't mean yours will so check the manual (different ROM versions for different countries can impact this :Canon in the USA and Canon in Australia often have subtle differences in the ROM image).
Conclusion
If you have to ask for a refund or replacement be nice to the seller : real cards can be duds as well, just because your card is a dud doesn't mean someone was trying to rip you off :for all you know the seller could be ignorant of what they were selling and never tested the card themself (or you could have a genuine dud).
I hope this helps someone find a good deal :there is another guide on spotting fake SD cards that is very good (with pictures) that I recommend you check out :it does have one factual error (it suggests you copy a very big file in excess of 2gb to the card : something that will rarely work under normal circumstances) but aside from that it is very good.
I will post a walkthrough of SD card troubleshooting if people find this guide useful."
I'll paste it here also in case it disappears from Ebay.
nupshutup says:
"Testing for fakes : SD cards, USB drives, MMC, CF and other portable or removable storage devices
As many people have reported there are a very large number of fake and counterfeit SD cards on Ebay at the moment. The reason for this is the large profits which sellers can make and the minimal import cost associated with such a high value item. Having spent quite some time contacting manufactures of SD memory cards in the course of my job I have been shocked to find that the vast majority are not only selling fake items but are very open about it.
To give you an idea of what kind of scale the problem is I contacted 45 manufacturers and wholesalers of SD cards throughout South East Asia :of these only 1 was able to provide me with proof that they held the correct Patent and Licensing for the production of SD cards. During this research I found numerous suppliers who got very upset when I suggested that selling counterfeit items was in any way wrong :the standard response was "We supply many people in Europe and US and there is no problem :they are making lots of money and are very happy" (quote lifted from an actual email).
Before you buy a card use you head:
1. While the physical appearance of the item is a good indicator the fakes are getting better and better. Remember that the act of printing a sticker is very simple and the casings are a dime a dozen. Look out for anything out of place such as misaligned stickers or serial numbers which have been badly printed.
2. If you are going to order a card don't trust a webmail Email contact address.
3. If you are going to order numerous cards order a very small sample first and refuse to pay a premium :often you will pay a lot for samples and receive "real" products then get shafted on the actual order.
4. If they are selling a large quantity and are in Australia ensure they have an ABN. If they tell you they are going to charge a premium for supplying a tax invoice consider that an insurance policy and just swallow it (or withhold 50% of the purchase price and send it to the ATO :as you are legally entitled to do).
5. If they have less than a 100% positive feedback rating then forget it :furthermore if they have never sold an SD or memory product before and instead have sold numerous very low value items in a short period of time consider them to be a High Risk (people do this to get their feedback rating up before cashing in).
6. Don't buy if they don't have a return policy. If you decide to risk it only pay what you are willing to lose ($12 for a 4 GB SD card is too good to be true but if you want to risk it remember you might get a 128mb card which isn't such a bargain).
7. Avoid sellers who charge high postage and handling costs :this spells disaster for you if you try to get it replaced because they will charge you the same amount again (the scam runs along the lines of : you buy an item for $3 pay $10 postage, it doesn't work so you send it back and pay another $10 to get it back to you :it still doesn't work so you ask for a refund, the seller happily refunds you money after you send the product back and they makes a tidy $20 and still has the product to sell to some other sucker).
8. If you must buy from someone who is profiting of high postage costs consider offering them more for the product in return for a reduced postage cost :this will save you if you have to send the product back and pay postage a second time.
9. Do your homework :recently 64, 128 and 256 mb Sandisk SD cards have flooded the market so the price is genuinely low (wholesalers getting rid of stock) but 1 GB and above cards are still not dirt cheap. Consider using an online price checker service such as StaticIce to find out what the going rate for the product is and then deduct a reasonable amount for retailer markup (5 :25% is a good guestimate). If you can't work out why a product is so cheap then it is probably fake :check Alibaba.com for suppliers of the product and email one for a price list (I don't think I am allowed to name names of known counterfeiters but lets just say that if the supplier has a hotmail address or other web based email address ... you fill in the blanks).
10. Once you have the product test it properly the first day you get it. If you buy a 2 GB SD card and it takes you 3 months to take 1 GB of photos there is a good chance the seller will either be long gone or ignore you when you complain.
Testing:
Most of these instructions apply to SD cards but can be used for other memory cards and USB drives as well.
1. If the card has a write prevention switch (as all SD cards do) put it in the Read only position and try to write to the card (if you can then it is a fake).
2. Reformat the card in you camera (if the card has an overstated capacity this will either fail or format the card with the actual amount of available space).
3. Copy a series of files to the card. Remember that most SD cards are formatted with a FAT file structure so files over 2GB can't be saved to them anyway. Try a series of 100mb files (recorded audio from Windows Sound Recorder found in the Accessories menu will do the trick, just record silence for ten minutes (no microphone needed)).
4. Copy a series of small files to the card :try text files or your temporary internet files. Do this until the card is full. (Testing capacity and the Master File Table).
5. If it is an SD card or similar put it in you camera and use the Video Record function :record for 30 minutes (or as long as you can) then wait for the camera to save the file. If the camera can't save the file and tells you the card is invalid then again you have a dud on your hands)
6. Attempt to open a large file directly from the card :a Photoshop file or even one of the silent audio files you recorded earlier will do the trick. You can usually connect you camera to you computer in Mass Storage mode to test this.
7. Use a program such as SiSoftware Sandra Lite (Free) to test the read and write speeds of the card. This software has built in benchmarks so you can compare the results to what you should be getting. This requires either a card reader or you camera to be connected in Mass Storage Mode.
8. Use KillDisk to view the contents of the card. Run the disk wipe on the SD card (which may fail with fake capacity cards) then view the contents again. When you scroll through the sectors move towards the end and look for changes that are out of place (the first 100 or so entries are the MFT and will be full of gibberish, then it should be all zeros :if it is 99 instead of 00 you have a card with overstated capacity).
9. Finally before you complain to the seller check that you camera can actually read the card :by this I mean many cameras can not handle cards with a capacity of over 512mb, just because you found someone on the internet whose camera could doesn't mean yours will so check the manual (different ROM versions for different countries can impact this :Canon in the USA and Canon in Australia often have subtle differences in the ROM image).
Conclusion
If you have to ask for a refund or replacement be nice to the seller : real cards can be duds as well, just because your card is a dud doesn't mean someone was trying to rip you off :for all you know the seller could be ignorant of what they were selling and never tested the card themself (or you could have a genuine dud).
I hope this helps someone find a good deal :there is another guide on spotting fake SD cards that is very good (with pictures) that I recommend you check out :it does have one factual error (it suggests you copy a very big file in excess of 2gb to the card : something that will rarely work under normal circumstances) but aside from that it is very good.
I will post a walkthrough of SD card troubleshooting if people find this guide useful."
