This is a great essay on the hidden, and possibly very large, costs of acting in reaction to our fears in ways that fail to substantially benefit us. He uses the example of TSA Security theater as an obvious case, but talks about a number of others.
As a concept, this is an important one for us to grasp. It goes hand in hand with our misperceptions of risk. Most people judge the risk of spectacular but highly unlikely events to be much higher than they actually are. The relative costs and efforts of fighting terrorism and car accidents is a great example.