http://kotaku.com/5486262/sonys-degradable-video-game-demo-patent
It is, to say the least, an interesting idea for demo structure. Personally I think it is stupid but what do I know.
There is some scuttlebutt (I love saying that) that this demo structure is part of Sony's current anti-piracy experiment which began with the release of the PSP game: SOCOM: U.S. Navy SEALs Fireteam Bravo 3 (I think was the titles name)