Let me respond briefly to some of the comments.
I do not know on what basis Mr. Fallows in the Atlantic Monthly believes that we have broken al Qaeda's operational capacity. Granted, we have seized or killed many of bin Laden's henchmen, and his sanctuary in Pakistan is less secure than his pre-9/11 sanctuary in Afghanistan, so it is fair to surmise that we have weakened al Qaeda. But the Heathrow plot suggests (though does not prove) that al Qaeda can still orchestrate a devastating, though fortunately foiled (well, al Qaeda's 1995 plot to blow up airliners over the Pacific was also foiled, and that didn't prove that al Qaeda had been broken), attack on the United States. It makes no difference whether al Qaeda employs British Muslims or Saudi Arabians to carry out the attacks that it plans.
I disagree with the comment that says that we should spend less on antiterrorism because terrorism kills fewer people than ordinary crimes. First, it is harder to limit terrorism than to limit ordinary crime; the terrorists are more determined and less deterrable. More important, the potential threat posed by terrorists in an era of proliferation is much greater than the potential threat posed by ordinary criminals.
When I said that our current expansive conception of civil liberties dates from a time we felt safer, I didn't mean to disparage the fear of nuclear war during the Cold War. After communist subversion in the United States was defeated in the late 1940s and early 1950s, we felt pretty safe from domestic threats, the kind of threats that put pressure on civil liberties. We no longer have that feeling of safety.
Finally, I was asked about profiling. I am not an enthusiast for profiling. Apart from the resentment it causes on the part of people (American Muslims) whom we very much want to keep loyal to the United States, it can be circumvented by recruitment of terrorists who do not fit th eprofile. More and more "white" Europeans are being converted to Islam and some of them may become terrorists. On the other hand, some limited, discreet profiling is efficient and I very much agree with the commenter who said there should be a "pass" from security checks for people who have security clearances or are otherwise certifiable as safe.