http://www.wisegeek.com/what-is-mob-mentality.htmThe term “mob mentality” is used to refer to unique behavioral characteristics which emerge when people are in large groups. It is sometimes used disparagingly, as the term “mob” typically conjures up an image of a disorganized, aggressive, panicked group of people. Social psychologists who study group behavior tend to prefer terms like “herd behavior” or “crowd hysteria.” The study of mob mentality is quite fascinating, and it is used to analyze situations which range from evacuations gone awry to the moment when demonstrations turn violent.
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When used in a pejorative sense, the term implies a group of people which has gotten out of control. For example, in a news story about a store sale at which people were trampled, the journalist might use “mob mentality” to describe the selfish behavior of the people who attended the sale. Such stories illustrate the desperate actions which people will involve themselves in during a period of resource competition; people may mob trucks with relief supplies, trample each other at big box stores, or riot in the streets in response to resource scarcity or a perceived scarcity.