I tried buying a memory card (16Gb?, I think) for my blackberry and tried hooking it up to the mac to use as an iPod. When syncing, it was going to take like 5hours or something to sync, so I unplugged the data cable (the RIM sync software wasn't great at quitting). Anyway, after unplugging the data card was corrupted, and I could only get it to reformat to be like 2Gb or something even on a PC or a Mac.
I think it's just the way they get toasted..