Jeffrey Veen has an interesting post over at his blog discussing a stream of Twitter data coming in while he was speaking at a conference. He says he felt as though he was cheating on an exam by "listening" to what the audience was saying as he was speaking. By addressing audience concerns as they hit the cloud, he was able to turn the audience in his favor.
I saw this phenomenon in action ad a dUx conference in Chicago a couple years ago. The speaker acknowledged that he was watching the Twitter stream while he was speaking and I think it actually made the presentation more rich. He was able to take short detours to address concerns of the audience without the disruption of someone raising their hand, being called upon, and articulating their concern.
In Jeff's case, he's considering the user of an audience advocate (or ombudsman) on stage to filter the stream and raise valid concerns on the audience's behalf. I think this is a brilliant idea to help ensure the presentation is as relevant to the audience as it can possibly be. While a lecture is informative, it's never as informative as a dialogue is. The more we can do to make our group interactions a dialogue, the more productive those interactions will be.