Originally Posted by
pWei
It could also be a fake. Fake Sandisks are rampant.
Unfortunately, this is completely true. And it's not just constrained to Sandisk branded cards.
Andrew "bunnie" Huang, hardware lead for Chumby Industries (they make cool alarm clocks) and hacker of the original Xbox, has a really great writeup on his blog about fake SD cards. It might be a little technical if you're not an electrical engineer, but the investigation is fascinating:
http://www.bunniestudios.com/blog/?p=918
One of my favorite parts, referring to shopping for SD Cards in a Shenzhen market:
Second, the small vendors are entirely brazen about selling you well-crafted fakes. Typically, the bare cards are just sitting loose in trays in the display case; once you agree on the price and commit to buying the card, the vendor will toss the loose card into a “real” Kingston retail package, and then miraculously pull out a certificate, complete with hologram, serial numbers, and a kingston.com URL you can visit to validate your purchase, and slap it on the back of the retail package right in front of your eyes.