Let me reply briefly to the main comments.
One theme in the negative comments is that if one profiles terrorists, or groups believed to be more likely to commit other crimes, the terrorists or criminals simply change whom they use, or new criminals replace those who are profiled. Sometimes that does defeat profiling, but not usually. Terrorists cannot change that easily whom they use since the supply of types willing to give up their lives to kill Americans or others is highly limited. Similarly, the supply of criminals typically has a limited elasticity of response. These considerations explain why the police "profile" ex-convicts, young people congregating at various suspicious locations, and in other ways. Are the critics saying the police should not be doing this? I doubt if they would carry that position through consistently.
Yes, we can spend more on various types of deterrence, but do we really want to search elderly women at airports as much as young men of Middle Eastern origin? (Let me add that my wife and her brothers are of such origin, and accept that they do get profiled.)
I recognize that being singled out for extra attention can be embarrassing. I suggested compensation for that. Someone mentioned that Steve Landsburg has also suggested compensation-good for Steve! Such compensation may not be sufficient to offset fully the damage from being singled out, but along with courteous and respectful treatment, it can go a good ways toward reducing the distastefulness of the process.
One last point. I work weekends in my university office when the doors are locked and few persons are in the building. I "profile" in judging whether to call the campus police by whether I believe a person belongs in the building- in fact I have called the police on more than one occasion. Do the critics of profiling suggest that instead of such profiling I call the police every time I see someone in the building-that is the purest example of no profiling- or every time I see someone in the building that I do not recognize, or when I judge they do not belong in the building, even though my judgment may depend on age, race, or other group characteristics?
This is not only costly, but borders on the absurd. I believe that the commentators who claim to oppose profiling do in fact profile in this and thousands of other situations. I do not know if this is true, but the media reported a few years ago that Jesse Jackson profiled when he heard someone walking behind him, and turned around to determine what group they belonged to!