We've been hearing for years that console manufacturers will try to restrict used games with their upcoming consoles, and now it's looking like Sony is taking steps to make that a reality. Last September, Sony filed a patent application for a technology that ties games discs to a user's account or a console's ID. Should this technology be implemented, it would mean that you won't be able to play games you purchased used, rented, or borrowed, which certainly isn't anything we want to hear.
The good news here is that a patent application doesn't automatically mean this technology will be present in the next PlayStation (or any future consoles from Sony for that matter). Indeed, Sony frequently files patent applications for new technologies that never see the light of day, so this could just be another to add the pile. Still, it isn't very encouraging to hear that Sony is actively pursuing new technologies that restrict used game sales.
With this system (as explained by NeoGAF user gofreak), game discs would be outfitted with a contactless RF tag that's capable of remembering whether your disc has been tied to your user account or console ID. If it has been, it won't play under another account or console, effectively blocking access to used games and, if adopted on a large scale, potentially bringing the massive market for used games to a screeching halt.
Sony's system could allow for a limited number of uses instead of blocking the content outright, meaning that if Sony is feeling generous, it could allow a number of additional uses on other consoles or accounts so you can let your friends check out the game. On the other hand, it could be used to get you hooked on a game right before cutting off access, forcing you to go out and buy a new, sealed copy if you want to keep playing. We'll have to wait and see just what happens with this patent application, but in the meantime, you can check out the full listing over at Free Patents Online.