Xen on 13 June 2013
Tretton has already clarified that here:
http://www.gamesthirst.com/2013/06/11/jack-tretton-clears-up-confusion-over-ps4-used-game-drm-stance/
"If you buy a used disc from GameStop, you’ll have no problem popping that disc in and playing it from your PlayStation 4. The issue may arise when you try to jump online and play with other players. At that point, a third-party publisher may impose a fee or not allow that."
There's another good link about another Sony exec clarifying, but I forgot his name and can't find it.
