my guess is that Sony would love to implement some kind of restrictive drm, but they don't have the balls to do it just yet. probably the drm-rookit scandal is still fresh in thier minds.
lets not forget Sony is also major players in the Movie/Music market and every year they and thier friends in the RIAA & MPAA whine and cry about piracy. that coupled with all drm patents they've amassed over the years... i think they are just waiting for the right time to implement.