In the end, who really cares about whether Mac OS X will be able to run on a PC? The only advantage would be convenience and accessibility to more software.
From a standpoint of selling computers, I bought a Mac because of style and included hardware, workmanship, and design. Unless I wanted to save money, I wouldnt buy a crappy Dell desktop. I would rather use the pieces-parts approach and make my own computer to my specs. I also wouldnt want to bother with hardware compatibility issues.
From an operating system standpoint, Apple would do well to make Mac OS X available to PC-computers, especially if Apple wants to become a software company rather than a full-fledged computer/laptop company. I am not really that well-versed in business and such, so I dont know how important this is.
I do know that it really doesnt matter if a bunch of computer geeks get Tiger to run on a PC. To me, it will have no effect. Apple makes a damn good computer and I dont have the time or inclination to convert a Mac into a PC or a PC into a Mac. Hell, I could peel an orange with most of the peel intact and wrap it around an apple and vice versa. But the apple still tastes like an apple and the orange tastes like an orange. The question is, which fruit do you want to eat.