Using Twitter to teach?

Bob Cargill, Meeting Students Where they are: Using Twitter to teach, picks up on an interesting article in the Chronicle of Higher Education on Professor Gets Religion about Twitter in Class. The article mentions that only 11 out of 80 students had signed up in the early stages of the class in question, but that he hoped more were to come. I have discussed this issue before (Using Twitter in the classroom) and have not, as yet, done anything much with Twitter in class myself. One of my reasons for this is that students don't actually use Twitter. Not yet, at any rate. Not many. Not much. Current undergraduate students, like High School students in the US and secondary school students in the UK, are massive Facebookers, but they think of Twitter as the preserve of middle-aged men ("I am sitting on the patio") and celebrities. I would have to see a major shift in student take-up of Twitter before I would be interested in experimenting in using it in teaching, and I am saying that as something of a twitter-holic myself (a middle-aged man and not a celebrity).