It supports ARM; and a bunch of ARM-based netbooks are due out soon. They are cheaper and much more power efficient than intel's Atom etc. And Windows doesn't run on them (yet). I'm not a big linux vs. windows or ARM vs. intel fanatic, but I'm excited at what seems to be a disruptive inflection point coming up in the next year or so...
Strictly incorrect, as Windows CE does run on ARM CPUs, and I'd wager that most first-gen ARM netbooks ship with Windows CE instead of Linux.