The ziplock bag is probably more protective than the dvd cases they use at gamestop. I'll never understand how people manage to lose the cases. I understand with cartridges.. i didn't keep any of those boxes.
Anyways, on subject, the clerks give me strange looks when I want to see the discs before I buy a used copy. Ofcourse they have the discs shrinkwrapped to the manual with the label facing out! Why am I going to pay $30 for a used game if it is scratched to hell?