Classic game theory thing. I think enough runners don't see the point of taking their turn if they don't know for sure that a competitor will. Hence why you see Puskedra/Albertson. Albertson was in his mind I like your pace, but I a) don't know if I take the lead, you'd then ever take it back b) you'd even run the pace I'd want you to. So he just did his own thing, and ran in front of and behind of people as the race dictated. There're plenty of people who will run behind a pack to conserve energy/avoid the wind, but far fewer who would then be willing to coordinate sharing wind-taking duties. You do see this from time-to-time in situations where there are team tactics (by nation, college team etc.).