Profiling
Having noted how easily "civilized" western nations in the last century were overtaken politically by homocidal maniacs, I have some reservations about improving the ease with which those inside governments can instantly find and persecute individual citizens impeding their goals.
There's a thread of criminality in the judiciary where I live, so this is not a totally abstract concern.
The reality, however, is that the few hallowed civil protections which limit government collection of databases 'profiling' citizens (in the U.S., at least) are largely illusory.
Although parts of U.S. government are prohibited from making such collections, many private sector enterprises do this as a matter of course. Between the demographically profiled mailing list databases for rent by the cash-responsive members of the Direct Mail Association and the incredibly nosey records maintained by credit rating companies such as Equifax and Thompson Ramo Woldridge (TRW) - a poster-boy version of a defense contractor on the government dole - little information about U.S. citizens is unavailable to those with pull or bucks. With the near-horizon advent of the networked electronic toilet, the process will be complete.
That said, one must observe that the standard infrastructure personal information compilation and storage processes tend to concentrate on the most stable and reliable middle-whatever folks who fall toward the center of the socio-economic matrix. The resourceful (tricky) rich, the indigent, the criminally minded, and other outliers can largely avoid the trail recording that follows us working stiffs.
So what the h*ll. You and I are already profiled til we squeak. It hasn't hurt much yet. Why not spread it around to the folks who are not on the radar?
When I applied for a student pilot's license a zillion years ago in a small European country that favors cheese, one of the gateway requirements was a "certificate of good character" from the local police station. At 15, I really hadn't had much time to develop a bad character but it was a new and interesting concept to ponder, and I have worked on it some since -- without much progress, however.
Everyone who gets to sit forward of the front lavs on an airliner has gone through a lot of filtering. Why shouldn't the folks in the back have a bunch of that also?
I don't believe that 'passenger registration' is inconsistent with efficient low-cost air operations. After a transition period, it would really lubricate the check-in and scrutinizing process. In fact, a 5-star luggage tag could add a degree of status to the passenger persona that would provide some bragging rights. Could provide a new kind of social register - a return of Woodhouse-style POSH for the excursion-fare set.
My net suggestion: In the computer era there is no such thing as personal privacy anyway, so let's get on with it and profile folks till they squeak. It's for a good cause.