This whole Multitasking thing is such a fallacy. You just can’t do two things at once. What you are really doing is time-sharing by switching between different tasks. When you are in that meeting, checking your PDA, you are not paying attention to the meeting. Even if you think you are “listening”, you really are not.
The Ban Blackberrys post over at Creative Class misses the point about having a Blackberry policy. What is really going on is that those constant Blackberry checkers (iPhone users are no better) are not engaged and contributing to the meeting. They probably don’t even need to be there. If the meeting is really valuable, then no one will have time to check their PDA.