Today's New York Times article "In the Lecture Hall, a Geek Chorus" is about people chatting online during lectures and talks, creating a side channel. Quotes from blogosphere luminaries - Clay Gillmor, Cory Ito, Joi Shirky, Dan Doctorow, etc.
people with laptops have realized that they do not have to sit idly during the presentations. Some people, of course, ignore speakers entirely by surfing the Web or checking their e-mail ... But others are genuinely interested in a lecturer's topic and want to talk concurrently about what is being saidI find people using laptops during meetings and lectures to be rude and annoying. We go through all this trouble to get people together in meatspace and then folks aren't paying attention, instead signaling that they've got more important things to do than what the group is together for.
But using chat technology to allow a side channel during a lecture does seem useful - it augments the meeting, it doesn't replace it. I particularly like the idea I first heard from Clay; project the chat room logs to the room so the chat becomes part of the event.