The short history of Anonymous as activist

http://mediacommons.futureofthebook.org/tne/pieces/anonymous-lulz-collective-action

"What we can note about Anonymous is that since the winter of 2008 it has become a political gateway for geeks (and others) to take action. Among other opportunities, Anonymous provides discrete micro-protest possibilities that aren't otherwise present in a way that allows individuals to be part of something greater. You don't have to fill out a form with your personal information, you aren't being asked to send money, you don't even have to even give your name but you do feel like you are actually part of something larger. The decision to engage in political action has to happen somehow, via a concrete path of action, a set of events, or influences; Anonymous is precisely that path for many."

This is a pretty good summary of both the history of Anonymous activism and their "structure."  Of importance here, it notes that "The uneasy relation between these two tendencies is partially resolved when anons constantly remind each other to refrain from behaving like a leader, and thus push participants to strive for consensus as the preferred mode of decision-making."