Sony was granted a patent for a multi-layer disc that could feature a BD-R or BD-RW layer. So one layer would feature content, like a game, and another layer would in an area reserved for storing user information, be writable with perhaps console and user data.
While the chip itself may prevent piracy, the ability for the PS4 to write console or user specific data would lock the disc to one or the other. In addition, the drive wouldn't necessarily have to be a Blu-Ray writer. The writable layer could be DVD-R/RW or CD-R/RW, as well as BD-R/RW. So the drive could feature an inexpensive red laser for writing data to a DVD or CD layer, rather than being an expensive Blu-Ray writer drive.
In my opinion this is by far the more interesting anti-piracy/second-hand measures as it puts all the information right on the disc itself rather than putting it on a database that can or can't be called depending if the console is online or not.
http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=1&u=%2Fnetahtml%2FPTO%2Fsearch-adv.htm&r=1&f=G&l=50&d=PALL&S1=08363531&OS=PN/08363531&RS=PN/08363531
