Crossfit is basically what used to be called "circuit training". Some dude from California thought up a way to market "curcuit training" to the kind of people who buy Macs, Ipods, Prius cars, Ikea... (i.e. trendy San Francisco yuppy faggots and bored house wifes). In my opinion it's dangerous with a high risk of injury. example: that kipping pullup bullshit they love to do. They have a pretty big injury subforum on their discussion board. Personally I think olympic lifts are useless, kipping is useless and anything involving inflatable balls is useless. Crossfit is more of a skill set than useful training. Olympic lifts are very skilled lifts, not muscle lifts. That's why the Clean & Press was dropped from the Olympics because athletes basically used skill to completely cheat the Press part.
Look at Greg Glassman (crossfit inventor) and then look at Ross Enamait, who actually practices what he preaches, and decide who you are going to listen to. www.rosstraining.com
Also check out http://www.moynihaninstitute.com/ for some funny stuff on crossfit, he had a great article a while ago but it's not on the page anymore.