There are some insightful comments on how moderation architectures affect the emergent character of social platforms in Chris Wilson’s article on Slate:
Digg, Wikipedia, and the myth of Web 2.0 democracy.

He explains how the rules structures of Wikipedia and Digg have resulted (ironically) in highly centralized power structures and territorialism. A quote:

While both sites effectively function as oligarchies, they are still democratic in one important sense. Digg and Wikipedia’s elite users aren’t chosen by a corporate board of directors or by divine right. They’re the people who participate the most. Despite the fairy tales about the participatory culture of Web 2.0, direct democracy isn’t feasible at the scale on which these sites operate. Still, it’s curious to note that these sites seem to have the hierarchical structure of the old-guard institutions they’ve sought to supplant.

He goes on to explain how Slashdot’s moderator-selection rules help to keep this top-heavy effect from happening, by making moderator status a bit easier to acquire, at more levels of involvement, while still keeping enough top-down oversight to keep consistent quality levels high.