SketchUp does not run in the cloud. The above example "Roozz" was scamware. It messed with the local install of SketchUp because it did install SketchUp locally into 'Program Files'.
"Spoon" is at least as clever to install unobtrusively into '%USER%\Local Settings', but it doesn't succeed to display the application inside the browser (it's displayed in a normal window).
Running a local app in a browser is really not the point of cloud computing (we do already run media plugins or pdf viewers in the browser; there exist plugins that can put any application inside firefox, also SketchUp).
Those plugins Roozz/Spoon don't give platform-interoperability. In the best case, such a plugin would create a VCN connection to a computer/server that runs those applications on a real Windows/OS X.
I think Google did good to remove SketchUp from Roozz (which is dangerous) and possibly the same for Spoon. On the other side, Google likes web applications and confirmed that they keep an eye on a future SketchUp Web App, when the technology is ready:
http://www.google.com/support/forum/p/sketchup/thread?tid=39d42ddba38c76b3&hl=en