Jon,
I think as JK pointed out, this is where "fast" players miss the point. They are often so damn rushed to get the round over, they don't take notice to what's going on ahead of them and the crest of carnage they leave in their wake.
The scenario I pointed out is not infrequent...it happens a lot at public courses, especially on weekends during the prime season. And as Sean and I both pointed out, a fast group trying to work its way thru many groups is only going to have a slowing effect on everyone else, who are already frustrated themselves.
P.S. I agree that one slow group can slow everyone down, I don't think that was ever in question. But if I'm in a 4 some, 5 holes (10 groups) behind that slow group, its not going to do any good to let a fast group play thru everyone because by the time they reach that slow group, the round is likely to be almost over.