After reading Sander's response to my post, I came up with a plausible reason for the adoption of Linux on the home computer.
If a Linux support company and a PC vendor (such as Dell) were to team up to sell Linux boxes, Linux could succeed on the desktop. The primary problem is that I don't see how Dell (insert favorite PC vendor here) would make money on such a move. Undoubtedly the expense for them would be in hiring support to handle the Linux PCs. I suggest that they could either sell that support off to Ubuntu, Novell, or Redhat. As long as they don't spend more than $6 per box, then they should come out winning. I say this, because I've read that they pay $6 per license to Microsoft for Windows. The only benefit I can see for Dell in this venture is that they would reduce the considerable burden of support for their PCs, one of the most difficult things for large companies to do right.
So that gets Linux to a place where a majority of people could use it. Dell would also have to create a joint advertising venture with the Linux Support Company (ubuntu) in order to sell that product. Ultimately, it could generate enough home user interest to actually capture worthwhile market share.
It's a risky venture for any PC maker to do, and it would no doubt cause Microsoft to reconsider their pricing structure with the vendor, so we may never see this happen. If I were Dell I would try to brand this line against the Apple OS X for two reasons. You'll be generating that same "this is better" mentality that Apple has been using against Windows for so long. Might even get Microsoft off the back of the PC vendor (Dell).