Srdja Popovic was one of the founders and leaders of the student movement Otpor!, which helped bring down Slobodan Milosevic's regime in Serbia. At Google's Zeitgeist think-fest, he talks about looking beyond the revolutions of 2011 – "One of the worst years for bad guys, ever."

Popovic lists enthusiasm and laughter as essential ingredients of people-powered movements; but perhaps most fascinating is a study he cites of the potency of nonviolence. Reviewing revolutions and struggles over the last century, Maria Stephan and Erica Chenoweth found that nonviolent struggle has a 53% chance of success. Once the struggle becomes violent, the odds drop to only 26%. Five years after a nonviolent uprising, there's a 42% chance that a durable democracy will be in place; after a violent one, the number is 4%.

Here's a great lecture on harnessing people power, from a man who knows what he's talking about: