“Second, people have a tendency to get acclimated to risk. As the physicist Richard Feynman wrote in a report on the Challenger disaster, as years went by, NASA officials got used to living with small failures. If faulty O rings didn’t produce a catastrophe last time, they probably won’t this time, they figured.
Feynman compared this to playing Russian roulette. Success in the last round is not a good predictor of success this time. Nonetheless, as things seemed to be going well, people unconsciously adjust their definition of acceptable risk.” (fromDrilling for Certainty, NYT)
Good article, check it out.