It's a good point, but I do suspect that if I were to look into it the kinds of people you mention: "nurses, doctors, teachers, engineers, programmers" who are

It's a good point, but I do suspect that if I were to look into it the kinds of people you mention: "nurses, doctors, teachers, engineers, programmers" who are on twitter would actually turn out to have their own blogs or have written a book read by an audience, and would be thought leaders in their field and such folk. Your average member of those classes are likely not regular users of twitter. Twitter just doesn't work if people don't care what you say - you have to already be a celebrity, with an opinion that 'matters' to people. " Twitter doesn't do a good job of surfacing different communities" Yes, but what I am getting at here is that they are communities in the sense of several important people in the field who all know each other and thats it. There simply aren't many 'average' people using twitter regularly, at least in the sense of writing thoughts and/or having conversations. "using Twitter is sometimes a useful way to get customer support. " Yes, thats what I was saying. I think it should not be this way - at least, the actual dedicated customer support of the company should be at least as effective as tweeting at them.