The problem is distribution. Not many people outside the technical/hacker community are even aware what Linux is, let alone Ubuntu. They need to have more hardware partners that aggressively sell ultracheap laptops/machines. Furthermore these partners need more low entry sales channels like radio shack, walmart, target, or even CVS where more middle class consumers have access to these machines.
I agree. Unless there is a significant push by OEMs, the Linux desktop will never see wide adoption. I wonder what were the reasons for Dell pulling their Ubuntu based options in the US? Inability to provide support, or was it a push by its main OS provider.