People have a hard time weighing the relative risk of different events that occur around them. For instance, when anthrax was distributed to several points around the U.S., people often had the fear that they might come into contact with the spores through their own mail.

Only 22 cases of [anthrax] illness were confirmed nationwide, with five unfortunate victims dying. Traffic accidents kill 115 people in the U.S. daily, but the anthrax incidents inflicted social disruption and psychological damage that traffic tragedies do not. ["Combating the Terror of Terrorism", Scientific American, August 2002]

There are many factors that influence this type of reaction in people, including fear of the unknown, media sensationalism and poor practical math skills and it isn't completely clear how to combat this type of fear. Unfortunately, the government's solution is to install futile and wasteful screening in airports. These actions by the government may help to ease the concerns of the ordinary citizen, but they do little or nothing to deter terrorists from committing more atrocities in the future.
10:04:49 AM