The concept is not so new: the stream. Personal, social, favourite, referred, everything is an ingredient of this video salad ball.
Hulu, Netflix, Spotify and IPTV prepared the market: about 10 million people watch web content on the TV right now!
A UX great feature: Leanback works only with arrow keys, because it's designed to be used from your remote tv controller.
Great crossweb design!