A friend of mine (my boss) recently purchased a 2GB SD card from SanDisk on eBay. The problem is it fails to work. I definitely concluded it was fake after calling tech support and being told that the card weirdly fails to have some data written on the back, like "Made in China" or a proper product code (his card had AS0612DH-L which doesn´t exist according to SanDisk).
We tried this card on a Treo 650, 680, T|X and it was not recognized as such.
This card only worked using a USB SD reader, a Canon digital camera and a Palm Zire 71.
Here are the pics just in case you see something like this around:
Check out the holographic stamp on the back. It actually doesn't exist on genuine sandisk cards.
This is the screen from my Zire 71 as it reads the card's info:
And this is what an authentic SanDisk SD Ultra II 2GB card looks like: