The Freakonomics guy is in trouble again, this time, for examining the ways terrorists might attack us. He's looking at the economics of the situation, the low cost, low risk investments a terrorist might consider to do the greatest harm and cause the most terror within the civilian population.
As you might imagine, there are some readers who are not very happy with his estimations, and have gone so far as to call him a traitor et al.
Thing is, I bet every numb-skull sending hate mail has read some Tom Clancy (especially the last 20 or so pages of Debt of Honor, published in 1994, if you really want chills), Patrick Robinson or any of the new terror/thriller novels on the bookshelves.
Or maybe the haters have never heard of something called "The General Staff" and something called "vigilance." A group of people just sits around and thinks of situations that may be dangerous to America, and the activity of knowing where danger may come from, respectively.