Crackers have turned their attention to Apple's OS X for x86 with an intensity I could not have imagined. Their goal is to make it run on x86 hardware other than Apple branded kit. So far, they have succeeded without much apparent effort.
I doubt Apple can implement any scheme to restrict their operating system to their hardware alone with a real expectation of success over the long term. Whatever they do will be broken, and probably sooner rather than later.
In my not so humble opinion, Apple will be forced to release OS X to all comers, and soon, to avoid losing literally millions of sales. There is a great hunger for their operating system in the computing world, but much less inclination to pay for it if Apple is not going to approve their use of it.
Apple does not wish to write drivers for all sorts of hardware. I can appreciate that. But they don't really have to do anything but approve drivers and they can charge for that, as Microsoft already does.
If Steve Jobs wants to become an influential player, instead of stay marginalized and labor as an idea factory for others to copy, this is his chance. It is not unreasonable to see OS X with a 20% market share in the 18 months after release. Sales of Apple hardware would grow, as well, due to the "halo" effect, much as the iPod has sold a lot of Macs since it's introoduction. Apple's almost universally acknowledged expertise at design could be used to differentiate their machines and justify the higher prices they seek to get for their products. And at over $100 a throw, OS X would fly off the shelves.
C'mon, Steve; Get with it.