Google could work with Dell or something to do this, and Google could even promise to stand behind Dell if Microsoft tries to retaliate in a way that almost nobody else (like RedHat) could.
(Also note that with yet another six months or a year of hardware development, the specs on these netbooks are going to be pretty good. These netbooks also won't be subject to the Microsoft XP "sell it with only 1GB" issue, or anything other netbook-hobbling plans Microsoft might concoct.)