Why It Works:
It's just the way human social behavior works -- if a message is repeated enough times, others will begin to accept it as a commonly held belief in the group. In fact, studies have found that if just one person repeats the same opinion three times, it has a whopping 90 percent chance of converting three different people in the group to have the same opinion. Holy shit, that's how both politics and conspiracy theories work, isn't it?
And Internet forums!
Researchers at the University of Michigan have come to call the phenomenon memory distortion, and it's basically a brain glitch where the interplay of repetition and assumption makes us form our beliefs around whatever opinion is the most familiar to us.
But what makes it so treacherous is the fact that all it takes to sway people's beliefs is one crazy person. Hell, it doesn't even work all that well with multiple people: A study on the phenomenon exposed one group to an opinion repeated by three different people, another to that same opinion repeated by one person multiple times. Incredibly, the group subjected to one single guy repeating the opinion was three times more susceptible to changing their own opinions than the others. Even when we actively register that it's just one person spouting bullshit, we're still likely to believe it.
Digital Vision./Photodisc/Getty Images