<< I think dell *can* offer linux on their machines because of precisely that. >>
if i remember correctly, dell sadly stopped shipping preinstalled linux on their desktop/workstation machines (at least their main lines). its still available on nearly all of their servers though.
linux already has a strong market share in the web server market. but do i think linux will go mainstream on the desktop? probably not for a while in my opinion, despite the accessibility of ximian gnome and other major linux distributions. but do i care too much about desktop market? nah, not realy. its a good desktop for me that interoperates with the rest of my windows PCs just fine for my tastes.