The economic theory of moral hazard is “the prospect that a party insulated from risk may behave differently from the way it would behave if it were fully exposed to the risk” (e.g. holders of car insurance may engage in riskier behaviour than non-holders, investors may take unnecessary risks if they expect to be bailed out in case of huge losses, etc.).
James Surowiecki—author of The Wisdom of Crowds—questions the validity of the theory, claiming that we may be overestimating the effect of moral hazard… if it exists at all.
The biggest reason that moral hazard matters less than it might is that it can operate only if people actively countenance the possibility that their decisions could lead to complete disaster. But it’s well documented that people generally, and investors particularly, are overconfident and significantly underestimate the chances of being wiped out. The moral-hazard fundamentalists argue that banks and other financial institutions will act recklessly if they think they’ll be rescued in the event of failure. But Wall Street was reckless because it never believed that failure was even a possibility.