Yeah, there's been a hot debate over this for a while. Basically, Apple would lose money if they allowed OS X on PC's, because then less people would buy Macs.
Some have done the OSx86 installation with varied levels of success. I tried it last year sometime, and it ran fine, but I had problems with sound card drivers and everything sorta dragged because my processor wasn't SSE3 enabled.
It was a fun project, but I don't think the computer was nearly reliable enough to use daily. I reverted back to windows on that machine.
Exactly. Microsoft is a software company. Apple is a hardware company, they make money through selling a great user experience on their OS, which makes people buy their machines.