What I really want to know about Twitter is whether anyone is listening. Obviously some people are, but if 50% of the people have only tweeted once or never, I

What I really want to know about Twitter is whether anyone is listening. Obviously some people are, but if 50% of the people have only tweeted once or never, I'm guessing they're not glued to their account. And within that top 10%, there's an awful lot of people who have so many thousands of followers that they can't be paying much attention. So that leaves the 40% in the middle...how many of those people are really paying attention? Is everyone on Twitter just shouting into the void?