Chrome OS.

It's perfect for Google, shows that all you really need is a browser and does it in a compelling way. But it's not going to be a success and I'll cast my lot in with those that predict that it'll get rolled into Android.
The reason I don't see it working is that Google won't use it. Google is a company of engineers, developers and hackers - what do they want with a computer they can't use to do that?
The Chrome OS team is designing and building a product for someone else. Taking things away is a great thing, look at Apple, but if you take so much away that it becomes a product for someone else and you're no longer eating your own dog food. That doesn't usually work out well.

I may be wrong, maybe the team is great and maybe they can overcome the obstacles, but I'll put my money on the best that will come of Chrome OS is that it's evolved into another product or as many are predicting, rolled into Android.