Since the explosion of the Internet

Since the explosion of the Internet in the 1990s, nu- merous researchers have focused on identifying unifying characteristics of online communities. Efforts such as identifying political factionalism [1] or recommendation networks [24] have provided unique, simplifying insights into the behavior of human social groups linked by electronic networks. Such insights are of intellectual and practical interest. Underlying this interest is the hypothesis that relationships and behaviors in virtual communities re ect similar phenomena in the real world, such as commercial proclivities, political leanings, and propensity for violence.