Jeremy Zawodny has mixed but generally positive feelings about not having laptops open in meetings, but I think he's actually going after the wrong point. What you really want is a "no distractions in meetings" rule - working on email, thinking about your vacation plans, or what you'd rather be doing at the time - are all detrimental to the effectiveness of a meeting.
If you can avoid distractions like email or feed readers, a laptop is an invaluable tool in making a meeting more effective. Almost every useful meeting I sit in these days involves constant references to documents stored in the cloud, real-time scheduling for follow-on conversations, and back-channel talk among participants. All of these, obviously, require a network-connected laptop available throughout the meeting.
Allowing people to keep their laptops open requires a certain amount of trust; namely, you're trusting that people will use their laptops to further the goals of the meeting, not to be virtually elsewhere while others are counting on your input and feedback. But a laptop is a great tool; let's not throw out the good with the bad.