MediaGuardian.co.uk Advertising Google 'listens' in to web TV habits
Still a white paper rather than a developed system, but this sounds like a strong system. Being able to identify what people are watching and then give them more content along the same veins sounds like a good idea (see Last.fm, Launch and others for music).
However, it does involve more loss of privacy. The way it's going for Google is that they will know what you're watching, what files you use on your computer, what pages you look at on your computer and how you use your money.
Slightly worrying? At the moment, the data is completely secure and none is shared with anyone. However, if Google is ever bought or becomes strapped for cash, there's a host of applications for data as granular as the data Google owns. Then what happens?