Here is my Theory of Meetings:

The purpose of a meeting is to efficiently transfer worry from one party to another.

I like it because I'm an engineer, and it looks like some statement about Thermodynamics, which means I can apply a semester's worth of theory to the problem of meetings.

I've been on both sides of the worry transfer. I've gone into the meeting wondering "Why are we having a meeting?", and come out Worried about what was someone else's problem (SEP). I've been horribly worried, written a 2-paragraph executive summary to my boss, and first thing the next morning the Worry has been transfered to the responsible parties. Worry is like Heat in the Thermo equations. But, if the problem still exists, more Worry is generated, and more meetings are needed to efficiently transfer that Worry.

The Pro, Con, and Pawn analysis helps. We know that heat differences can be used to generate work, and the Plan is the analogous way to efficiently convert Worry into Action. Without the plan, you just have Cons generating Worry, and it gets transfered, inefficently, to the Pawns and (to a lesser extent) the Pros. The Pawns can't do anything, so they go home and have a Meeting with the dog (involving mostly kicking), who chases a squirrel, and thus the circle of life continues.

ShadowSystem's comments put him solely in the permanent Pro category, a near-ideal sink for Worry. These perfect sinks hate meetings, because they never bring Worry to the table.