An obvious source of social influence, of course, is social networking, the rapid rise of which has demonstrated the ability of anonymous peer-to-peer interaction to influence behavior. This occurs because social networks forge what Damon Centola, assistant professor of behavior and policy science at MIT, calls "weak ties" that, despite their moniker, actually increase the diffusion rate of behaviors and ideas. You may not have had a friend living in the Middle East during the Arab Spring, for example, but you likely had a friend of a friend. Put another way, it's a small world after all.