There's an obvious solution: Get people to write down their questions on paper from which the speaker can select questions that are of general interest and to which he has a useful or interesting reply. To keep some excitement, you can even get the audience member to ask his question at the microphone (with the understanding that he has to ask the question he composed on paper).
I'll grant you that this wouldn't be appropriate for every kind of Q and A. Unwelcome questions would be suppressed in the White House briefing room, for example. But it should be fine for technical conferences.
The idea seems so obvious (and beneficial) that I'm wondering why nobody does it -- at least at any conference I've been to.
Everybody gets a question card as they walk in. At any point you can fill it out and pass it down for collection by volunteers. Somebody sorts them and hands them over to the moderator (usually Stewart Brand) who, at the end of the talk, sits down for a Q&A with the speaker.
It works really well. The moderator asks a mix of audience questions and follow-ups, plus asks a few questions of his own.
I strongly recommend the series. In person if you're in SF, and otherwise via podcast.
I'll grant you that this wouldn't be appropriate for every kind of Q and A. Unwelcome questions would be suppressed in the White House briefing room, for example. But it should be fine for technical conferences.
The idea seems so obvious (and beneficial) that I'm wondering why nobody does it -- at least at any conference I've been to.