I haven't known any untruthful flashdrives, until just recently when I purchased a 4.0 gig non-brand drive.  I usually make sure I get what I purchased, so when looking capacity up through right click "properties," it showed the capacity of 4 gig, BUT I didn't think to investigate much further, except start using it.  Weeks later, I had 1 gig of memory on it, and separate folders, but one was empty when it should of had music.  I tried adding more music and some songs, and they showed up on the flashdrive fine and played fine.  Once I unplugged and replugged flash back in, it was gone, except the folders. 

Note: I also changed the name of a folder that had programs in it, and they too disappeared just instantly with no warning.

WHAT YOU SHOULD DO ALWAYS IF YOU EVER BUY A FLASHDRIVE AT ALL NO MATTER WHERE FROM: 

1.  BEWARE of too good to be true prices on these products (ask buyer if its used to see if it works right)

2.  Test their entire capacity, not just part of it like I did.  Basically, I bought a 1 gig with 3 unworkable gigs.

3.  Make sure you test flash on more than 1 computer to see if encrypted files transfer properly. 

4.  Don't wait a week to test.  No seller wants to hear bad news a couple weeks down the road. 

Hope this helps.