Last month's Atlantic magazine (I read in the spirit of "know your enemy") had a thought piece that was supposedly a lecture on the state of the war on terror from 2010, written by Richard Clarke, "Ten Years Later."
http://www.theatlantic.com/doc/prem/200501/clarke
Clarke speculates that the up-ramping of terror in the US by a series of coordinated attacks on malls. Which caused us all to stay home out of fear and which caused the US to tumble into financial disaster.
The way those snipers locked down Washington, I have no doubt that a well-planned series of attacks around the country would put a chill on people's shopping habits. Probably be good for online shopping though...