A few years ago, there was a fairly large group of Linux advocates who thought that marketing a Linux OS was folly. I was one of those people.
The argument goes like this: Linux and the UI layer needs to be OEMed by hardware makers. The hardware makers need to test it for their machines and offer all services, hardware, and software for their products. In essence, every OEM is as vertically integrated as possible. It's not significantly different from Apple's business model. Apple would be happy to funnel all of the software for OS X through an App Store just like they do for the iPhone (and in some ways, music through iTunes). Apple sells hardware, too. If the average Apple owner wants a wireless router, he buys an Airport.
I saw a bit of this while I was in between 2003 and 2004. Manufacturers each had a customized version of Linux, or maybe a rebranded popular Thai distro. Because hardware support was not as good as it is now, the OEM offered certified peripherals for the boxes.
Where does that leave distros like Ubuntu? They become contractors, outsourced from the OEM. They do OS customization and hardware testing for the smaller OEMs that can't do it themselves. There is probably even a market for Canonical having standard application and hardware stores that are rebranded for the OEM. The equipment and software comes from Canonical, but the customer sees only the OEM.
That was the argument, anyway. It could work. No, really.
Update: Xandros seems to agree that it could (and does) work. They've doubled their employees since last year.