Cringely offers an alternate theory for Apple getting in bed with Intel:
Microsoft comes into this because Intel hates Microsoft. It hasn't always been that way, but in recent years Microsoft has abused its relationship with Intel and used AMD as a cudgel against Intel. Even worse, from Intel's standpoint Microsoft doesn't work hard enough to challenge its hardware. For Intel to keep growing, people have to replace their PCs more often and Microsoft's bloatware strategy just isn't making that happen, especially if they keep delaying Longhorn.
Enter Apple. This isn't a story about Intel gaining another three percent market share at the expense of IBM, it is about Intel taking back control of the desktop from Microsoft.
via Dan Gillmor's blog