I think the idea behind a 'web OS' is horrible. Web apps are good for certain things: mainly presenting and manipulating text. Once you get outside of that small domain, you need much richer interfaces, and the web just doesn't present that. In fact I'm not sure it should.<p>The browser is a great platform for certain things, but everything doesn't belong inside of it. It shouldn't be an OS. Web OSs aren't that attractive to the consumer - they can just as easily visit multiple websites in several windows, and they aren't that attractive to developers - web development is relatively easy, and you lose a lot of power once you start developing on some web OS API vs doing it yourself.<p>I just can't see these services catching on.
I don't think it's a good fit for the web. The level of abstraction is at the wrong place. The web is an OS. The home page sites like Pageflakes are much more a WebOS than the sites cloning old-style desktops in Ajax.
I think there is potential in Web OS. But they can't be a defacto replacement of the desktop interface. I think the wufoo approach is better than say the youos approach.