Though I don't watch TV so this isn't directly applicable to me, after seeing it written out I'm amazed that this isn't already common. It's a really good, sensible idea.
It sorta happens with certain shows already, just on Twitter.
For example, in the UK there's a business show called Dragons' Den where people pitch for money for their crazy business ideas. Quite a large number of people tweet about the show while it's on and almost everything that happens. Not quite "chat" though.
