I just had a brainwave today. I bet their OS is going to be a distributed cluster, using your CPU during your computer’s idle time. It may even use your computer as a redundant Google File System node to offload bandwidth from Google’s servers.
This would explain why they feel the need to release an OS in the first place.
The future of course, would be having intense applications like games run on the worldwide cluster, with your computer only getting a VNC-like portal into what’s going on in the actual application.