The "Apple model" is changing. If Apple fails to make a version of its OS available to the Wintel public, it will take decades to reach market parity with Windows. Not releasing Mac OS X on the Wintel world to save Apple's hardware division would be like cutting off the nose to spite the face. By opening up the Mac OS X market to all Intel boxes (and I assume AMD boxes as well) Apple will be in direct competition with Microsoft. That has never been the case.
The central advantage of Windows (that it can be installed on a wide variety of boxes) would disappear overnight. Reliability could be at least as good as Windows, but without the viruses and spyware. Those who wanted the ultimate in stability and style could still buy a 100% Apple system. The important thing is that no sane IT director would chose to keep his computers on Windows because the cost of changing would be software alone, i.e., their hardware could sit still. Then Apple gets a real crack at the corporate market. Then Bill Gates will be left with a pile of worthless paper in all his Microsoft stock (he'll still be rich because he has steadily divested his MS interest, but think of all the new fortunes to be made in Apple stock!!).
This is not a redux of the clone fiasco, because Apple is not licensing its OS to new developers to expand its market share. It is (or could be) launching a frontal attack against Microsoft's market share.
Apple's hardware division will not die, in fact its longevity will be guaranteed by a Wintel-compatible Mac OS. Witness the Xbox; it is a billion dollar negative entry on the MS balance sheet - and little more than a blip in comparison to its big brother Windows. When Apple is the standard OS, think of the R&D dollars Apple will have to spend on its hardware.
This could be the start of something profound.