I think this is where things are headed. A Twitch streamer interacting with the chat room is like a step beyond Youtube with static comments, web/email forums, IRC/instant messaging. Twitch or something like it will probably expand beyond games, maybe not to general streams like Justin.tv, but to entertainment generally. Like the other day a gamer was pointing out how it could be cool if someone could stream a movie and the chat is doing their trolling thing through the movie.
I try to imagine what's beyond that. Rather than a mostly-one-person broadcast with interaction with the anonymous text that is the chat, maybe more like you see sometimes with role-playing streams where there are 5 people on screen, except now the entire chat can somehow feature on the stream (obviously there are difficulties with that). A kind of virtual pub, I guess. Maybe that's not much different than MMOs, though.