Google just patented Chrome OS, but the tone of the patent is much more than that. Google may have, in fact, received a patent that covers client cloud operating systems in general.
The patent is entitled "Network based operating system across devices
" and was filed in March of 2009, about two months before Chrome OS was officially announced. What makes this patent special is the fact that it covers virtual all aspects of "providing an operating system over a network to a local device" in a manner that would apply to any cloud OS that uses software other than a web browser. And even the web browser, as an entity that is regularly updated and would, conceivably, fill the role as operating system framework, would be touched by this patent.