Rumor: Linux and Steam running on PS4 firmware 4.0
Marcan42 of Fail0verflow fame was at the CCC33 event this year, to explain how Fail0verflow exploited the PS4 hardware in order to run Linux on the PS4.
The presentation goes back to all the pain the hackers had to go through in order to make Linux compatible with the PS4 architecture, which Marcan42 described several times throughout the presentation as "not being a PC" as it lacks lots of the legacy architecture bits required for a computer to constitute what is known today as an IBM compatible PC.
Be sure to watch the actual presentation. It's quite informative and detailed.