From now on, whenever I moderate a conference panel or otherwise organize a conference, I will make a rule that all speakers must make an MP3 of their talk before the conference and E-mail it. While it woudl be a good idea to then listen and see how good a speaker they are, the primary purpose is to get an idea of the length. The speaker, recording their talk at home, will notice that their 20 minute talk takes 35 minutes, and cut down the number of slides until it fits a little better. If not, and they mail in an 35 minute MP3, you can tell them what will happen at 20 minutes.
Not that I haven’t gone over time myself. Many speakers can use the discipline. And it’s a shame for both speaker and audience when you find yourself having to skip the final parts at random to stay on time, or if you don’t, eliminating time from other speakers, from questions or from hallway break conversations, which are the most important part of almost any conference.
Many conferences have a screen counting down time for a speaker, which is fine. The same idea needs to apply with questions. Along with the microphone, hand each question asker a 30 second hourglass to hold up while they’re asking. Sure, if the question is interesting, let them turn it over. But if it’s boring, say “thanks” and move on. And give a slightly longer hourglass or timer to each panelist answering the question. Again, not to be a den mother, but to have a chance to move on if things are not going anywhere. (Kathryn suggested the actual egg timers.)