Sony officially states that PlayStation 4 will not have DRM against used games

[AgentZorn]

According to Yoshida, "At a roundtable this morning, Sony's game studios chief, Shuhei Yoshida, told reporters that any requirement for users to register a game online in order to play it would be left to game publishers. Sony won't require that."

Well it's agood thing that Sony won't block used games but 3rd party publishers probably will.