Y'know, I think this is good. What this does is create a "lowest common denominator" for new users that's -better- than windows -- and that includes being locked down.
Provided Google provides a hardware switch(or cheap module) that allows rooting, Google will have acomplished two goals:
1. Newbs(and noobs) who are technically illiterate won't be able to screw things up. They also won't be able to do -everything-, and will be forced to actually learn in order to do things outside the nominal scope of Chrome OS.
2. Technically literate people will be able to modify it however they want, provided they care and can do the research to figure out how.
This will end up creating a slightly larger divide over the next few years - People who want things to just work will have it work; systems administrators won't need to worry about their users breaking stuff as much.

Now, if it was anyone -but- google doing this, I'd be afraid for the future - Google, however, has the smarts to think long term for their stratigies, and as such aren't -quite- as dangerous as, say, Microsoft or the MPAA are.