What if...

Mac don't usually freeze, and when they do, you have to send them back to a service center. On the other side installing a pen pusable reset button is not a problem or adding a watchdog timer. Many hard realtime systems use watchdog timers, that perform a hard reset when they are not cleared periodically.

What is interesting is that it looks like apple managed to make macos-x portable enough to allow it to run on different types of hardware besides ppc and x86. The integrated nature of the iphone comes from the fact that it's target audience don't know what is a battery or a sim card, they just need a device that just works and they have the money to have skilled service personnel do such things as swapping out a battery. The iphone, like the xbox360 will be more of a service rather than a product.