Robert Cialdini, in his book Influence: The Psychology of Influence writes about a concept called social proof. He writes that the concept "states one means we use to determine what is correct is to find out what other people think is correct." It's a fascinating concept and seems to be one most social groups are built around. It often leads to productive behavior and systems. But it's also how we sometimes end up with the "madness of crowds," which is when groups of people act irrationally and sometimes even violently despite most individuals in the group not normally behaving in such ways. It's something to think about.