The next time your are fixing some relative's or co-worker's machine .. think about if maybe everyone would be better off if they had a chromebook.
The point of these things is that, if you just limit things to the web, you can make a very secure, reliable, no-brainer type machine.
It can't do everything, but jeez, it sure can do a lot of what most regular people use their computers for, and that's just going to become more with HTML5 et al. Or a business could hand them out for employees who need some web app to do their jobs. You just have your login to the app (google hosted, or somebody else .. it all works), and if they break the machine, you just hand them another one. Data is cached on the device, but the real data is the cloud. The software on the device is designed deeply to be very secure (easier since it does so much less) so it should be much less vulnerable to "infection" the way a more general computers are.
Android and iOS are trying to not be vulnerable to malware, but it's so much harder when stuff can get installed. The chromebook does not have a native software "install" .. it's just the web, so it's a lot easier to nail down right.