Laptopless meetings
Tom Keating wonders about the pluses and minuses of forbidding people to carry laptops to meetings, but I think the whole controversy revolves around the reasons we have meetings in the first place. At Microsoft we probably would have to stop meetings altogether if they banned laptops -- I know you wouldn't get me to come.
Since switching to OneNote, I never carry paper notes, so a laptop is indispensible for me, whether I'm paying full attention to the meeting or "peeking" at my emails.
A meeting of more than two people should provide a net time savings for everyone, by cutting down on the number of one-on-one conversations necessary to impart information. If you're having a face-to-face conversation, a laptop is a distraction, but the minute you have more than two people in one place, some of the people will be more involved than others. A meeting is all about saving time.
The best way to prevent people from zoning out in your meeting is to make it important and relevant for them to participate.