Artificial Genocide?
If societies can order themselves systematically but unconsciously, it stands to reason that they can also disorder themselves systematically but unconsciously. As societies, the Balkans, Rwanda, Indonesia, and South Central Los Angeles have little in common, yet all have experienced, in recent memory, sudden and shocking transformations from a tense but seemingly sustainable communal peace to communal disorder and violence. Obviously, riots in America are in no way morally comparable to genocide in Rwanda, but what is striking in all these cases is the abruptness with which seemingly law-abiding and peaceable people turned into looters or killers. Scholars often use the metaphor of contagion in talking and thinking about mass violence, because the violence seems to spread so quickly from person to person and neighborhood to neighborhood. Yet sociologists who have studied mass behavior have learned that people in crowds and groups usually remain rational, retain their individuality, and exercise their good judgment; that is, they remain very much themselves. The illusion that some larger collective mind, or some sort of infectious hysteria, has seized control is just that: an illusion. Somehow, when communal violence takes hold, individuals make choices, presumably responding to local incentives or conditions, that make the whole society seem to have suddenly decided to turn savage. Might it be that rampant violence is no more the result of mass hysteria than the rampant segregation in Thomas Schelling's artificial neighborhood is the result of mass racism?
http://www.theatlantic.com/issues/2002/04/rauch.htm