The same guy who was responsible for unlocking the iPhone has come forward to say that after 5 weeks of effort, he's exposed a hole in the PS3 security.  Through this hole, he expects hackers to be able to start running unsigned code, which can lead to homebrew and pirated games (although does not condone illegal activities).  This effort, he says, is to open up the system so people can use it how they want, not necessarily how Sony wants.
While the media is going hyper over this news (it even got onto the BBC news), some experts think this will go nowhere.  While they agree he found an exploit, they feel it's a useless hole that accomplishes nothing.
Since Sony's PS3 security architecture is multi-tiered, I'm inclined to agree with the experts.  This guy was able to do something he shouldn't, but that doesn't necessarily open the door to a full blown hack.