What you think you know is wrong

In the absence of publicized regulations like traffic laws, the elevation of shared knowledge to common knowledge can be unpredictable, even chaotic. Outlandish fashions, surprise bestsellers, dark-horse candidates, currency hyperinflations, and asset bubbles and crashes are all cases in which people behave according to the way they expect other people to expect other people to expect other people to behave. The craving for common knowledge can even lead to a false consensus, in which everyone is convinced that everyone believes something, and believes that everyone else believes that they believe it, but in fact no one actually believes it.

From "Usage in The American Heritage Dictionary" by Steven Pinker.