I agreed that this is indeed a problem, but putting in a ban seems to be taking a step that puts the emphasis on the meeting chair, rather than the participants. (I agree with the point that Liz Williams made here.)

The source of the problem is simple -- poor individual practices.

If I am in the meeting, then it deserves to receive 100% of my attention, with no distractions. Otherwise, I ruin its purpose, hamper my own participation, and slow things down for others (the same goes for coming in late) when I distract myself with anything that takes me away from the meeting's purpose.

A meeting with everyone at 100% attention, should last a shorter time than one with bits and pieces of attention here and there, and should be of higher quality.

A participant who doesn't know how to manage their attention needs some training in how to get themselves into the flow state more often, and how to maintain it. Otherwise, they ruin meetings without even knowing it.

This training is sadly lacking, even as the number of distractions has increased, and will only increase in future.

Unfortunately, more powerful, smaller and less epxensive PDA's are the wave of the future. Without this kind of training, meetings will only get much worse.

The irony is, this is an excellent example of a case where more technology is leading to less productivity -- in the same way that a gun in the home can lead to less security.