Sony's PS4: patent and used games
It's amusing how various blogs chose to interpret the patent Sony has filed in the most speculative of ways -- its relation to used games resale. The RFID (NFC) chip to be embedded into the media (bluray, etc) will allow the console, or more precisely the remote server communicating with the console over the Internet, to authenticate the disk. Thus, the disk will serve as proof of authenticity (patent calls it "permission tag"). A technology on which this authentication is based can be PUF (Physical Unclonable Function) or a cryptographic key.
While it's possible that Sony MAY choose to use the RFID tag to _permanently_ link the physical media to an online account, it is insanely speculative.
It's plausible that Sony will use the tag to simply ensure that no pirated copies of the game enter circulation since cloning the physical tag is much harder than copying digital content alone. Additionally, even if one wanted to link the RFID tag to a particular online account, then it should also be possible to un-link it prior to resale. All it means is that at any given time, there can only be one account linked to a particular RFID tag.