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Well, I'm imagining it, and I don't see the point. It's ok, I guess; but why would I want to do this over the television set? When you watch TV, you want to watch TV, and little else (except perhaps eating popcorn). When you want to interact, you use your computer - which is probably not that far away from your TV set.
Plus, I don't see how this beats mobile social networking. We've got all these beautiful devices with large screens like the iPhone and G1, with fantastic social networking applications developed for them. With a TV, you're stuck in one corner of the house. With a mobile, you can go anywhere and carry the social network with you.