It looks like in-home streaming is coming to Steam and will be called "Steaming". This will allow you to stream games from one PC to another and shows the direction that Valve is going and once this is smoothed up, will be a key feature of SteamOS and will help you get all of the Windows Only games on your Linux-based Steambox. Right now, it's burried in the latest update, but doesn't seem to work anyhow. It's coming soon, so stay tuned.
An update to the beta version of the Steam client adds an early look at the computer-to-computer streaming that will be an integral part of Valve's SteamOS and Steam Machines. The option for in-home streaming, which requires some "tinkering" to access, according to the unofficial Steam Database, doesn't appear to function yet for users, but offers some insight into Valve's plans.