Someone probably already said this

All sorts of people are freaking out about racial/ethnic profiling in "randomly" searching bags in subway stations. Now, I'm sure it's true that most of the likely terrorists are from the Muslim world (not that Afghans, say, are easily identifiable as "middle-easterners," and brown people can un-brown quite a bit if they stay out of the sun), but does no one remember that the second most deadly terrorist attack in American history was committed by guy named McVeigh?

That said, here's something I haven't heard any one else say. Suppose we are successful in suppressing terrorist attacks of the London Underground scale. Suppose we stymie attacks intended to kill even 5-15 people. Then we've limited the body count of a successful terrorist attack to 1-2 people at most. Living in America, that isn't terribly frightening. An illin' heroin addict is probably just as likely to get you as a terrorist. But the point of terrorism is to scare the shit out of you--so how are they going to frighten you? I draw your attention, then, to the possibility of random acts of torture. It's easy to make a good approximation to napalm in bottle, squirt it all over an arbitrary white guy, and set him on fire. What do you do to stop that?

I'm just taking the long view here.