Linux hasnt "caught on" mostly due to the hassle of getting everything working just right. No matter how simple people claim versions of linux, such as Ubuntu, have become, Linux is still a bit of a b**** to get it running with the convienence and overall "greatness" that users are used to in commercial OS's such as windows or OS X.
Agreed, so far in netbooks the Linux installs have been half-hearted at best, although the initial Asus desktop on the EeePC 700 series had some thought put into it. Ubuntu and Intel are working hard on Ubuntu Netbook Remix and Moblin, but there are still too many bits of proprietary hardware out there that the manufacturer doesn't want to give out specifications for. Not things like graphics even, but standard run of the mill things like microphones and wifi chips.
Google can hopefully get it's Linux+Chrome OS onto hardware that is fully supportive of their OS. In addition they probably won't cry about using binary drivers as well. I personally think they should use FreeBSD, but its ARM port is probably less mature.
I can definitely see my current netbook (HP2133 - Linux doesn't support the microphone, nor video decode acceleration, because of the proprietary VIA hardware, and VIA supposedly support Linux, like hell they actually care) with a nice ARM based ChromeBook with 10 hours battery life next year. 1.5GHz dual-core SnapDragon please!