I think the problem is that to have a slick, user-friendly UI that doesn't get in your way with latency caused by inadequate performance, you need enough performance that doing thick-client stuff is trivial, and there's no reason not to include it.
I think if you used the SSD to hold a fairly large cache of applications, you could practically work "in the cloud" a bit like distributed RCSes (eg. git) do, and re-sync everything when the laptop can connect. You can still have backgrounded automatic update of the cached apps, and you can manage the cache completely automatically (or allow more power to users to "pin" data and apps to the cache). I haven't used ChromeOS before, but if it's on its way to working like that (TFA suggests it isn't there yet), it would be workable for some use cases.
I'd also like to see some open-source web apps rise to fame, I'm sure most companies deploying these things would be happy to contract with Google, but for government work or running a small company that competes with Google, I'd prefer to recompile the OS to point at a privately-managed cloud (which would probably be as simple as a couple of clustered web servers and maybe a DR site)