Oh, I need to make this point, because pople will believe, like Vicki Davis, that "All presentation backchannels should have moderators." The thing is, you can't moderate backchannels. You can control what's displayed on the big screen, if you want (and if your audience is squeamish, you may want to). But you can't control what's said on, say, Twitter. Just. Can't. That said, I agree with her that "a chat room is so much better for this anyway because it can be archived and allows more meaningful conversation and more extensive replies," which is why when I was doing it I used my own chat room. People still chattered on Twitter, though (next time I'll aggregate the tweets into my chat room).