Oh shit, I guess I best avoid buying a used car, and used Vinyls. If this tactic of serial keys were to work it'd have to be in either A) A steam form, which I wouldn't mind as I never sell games anyway or B) A 1 use CD key, which would mean anyone suffering a hard drive crash would lose all their games with no chance of recovering them. If they went for the second approach that would be stupid, besides, if there was a ban made of trade ins at game stores then people would just lend out the games they're not trading in, damaging the store and the company.