"The difficulty in early warning, among other things, is that if you give correct warning and act in response to that warning, the attack will likely not materialize (i.e. if the US knew Japan was about to attack Pearl Harbor our defensive preparations would prevent Japan from following through). This means that successful warnings are under-counted because the catastrophe never emerges. This tends to weaken early warning systems as they are perceived to be ineffective even though they may have averted serious problems.

The economic analogy is regulation. Regulations were seen as unnecessary and dismantled because there had been no crises, but policymakers failed to consider that there may have been no crises precisely because of the regulation."

-- Jamison Davies