Jon Udell has it. (This from the guy who wrote "Practical Internet Groupware", of course). On Reed's Law: "There's no free lunch; it always costs something to form communicating groups. What's becoming clear is that we must identify those costs, and begin to think architecturally about how to reduce or reallocate them".
And - the first time I've seen this so concisely - "There is another kind of cost, though, about which we know much less. I call it the cost of context assembly, and it is the bane of all groupware systems". This is exactly the problem addressed in my CPC model for Groove applications.