I've heard they are going to only let it run on specific hardware - that is, hardware that has got security verification. this is to prevent Macintosh's to be used on other X86 hardware.
although it might be likely that somebody will crack OS X.
that would be a pity though, because then people might not pay for it, when it is a much better OS than what Microsoft has made. IMO OS X is actually worth what it's selling for.