Recently, I had been seeing something too good to be true. 16GB for less than USD$1!!! Yes, anything thats too good to be true, probably is not. It seems that international scammers (mainly from HK/China though) is basically using some hack to change the flash drive FAT table to make it look as if it is really that big where in fact it is only really 1 or 2 GB of real capacity.
There is this article that explain a simple way to test it:
Or back to the good old days, you can simply delete the partition table and recreate, it will show its true form.