The summer of 2011 will be remembered in some cities for the riots that perturbed the public peace. The British riots got most of the headlines, but Chicago, Washington, and especially Philadelphia were the scene of violent and, to many, puzzling “flash mobs” made of up of young city-dwellers coordinating their activities and attacks via social networks and cell phones. There’s been no shortage of ink devoted to these events, but an article today on The Atlantic’s Cities website goes deeper into the phenomenon, largely with the help of Penn’s Philippe Bourgois and Eric Schneider, who shed light on the issue from anthropological and historical angles, respectively.