I got frisked by the Portland airport TSA folks. Somebody forgot to tell them that modern batteries and explosives are mostly the same thing. They saw my four-NiMH-D-Cell battery box on the x-ray, and thought it was Semtex, a plastic explosive. I think their chemical detector also id'ed it as Semtex, but nobody ever explicitly said that to me.
While they were gingerly pawing through my possessions as if they might explode, I noted aloud how disconcerting it was to see them pawing through my possessions as if they might explode. Somehow they turned that into some kind of bomb threat, because they called down their manager, the airport administration, the Portland police, and a Delta representative on me. While I'm not stupid enough to bring up the subject of bombs at airport security, watching somebody act as if my stuff might explode weakened my resistance to said stupidity.
It was only about a half-hour delay, however, it was a half-hour during which seven members of the security infrastructure paid sole and exclusive attention to me. It's obvious to me that I was a false positive. It was less obvious to them that I was a false positive; nonetheless I was a false positive for their tests.
One thing that economics teaches us is that you can't do everything at any one moment. At any one moment, the resources available to you are limited, and you must choose how you wish to allocate those resources. If you do one thing, you cannot do another. If you chase down a false positive, that leaves less resources to deal with other positives. Computer security folks are well aware of denial of service attacks. I think that the Transportation Security Administration folks are less aware.
Let's say that I wanted to get something through security. The best way to do it is to try sending pristine folks through security in a way that will trigger a false positive. While security is dealing with them, they go through security themselves, to find out what level of false positives are needed to overwhelm security. At some level, the security folks are likely to start sending people through with decreased scrutiny.
Of course, the whole increased airport security thing is a moronic waste of time. No hijacker would dream of hijacking a US airplane. Everyone would assume the worst, and fight the hijacker for their lives. There was a reason why there were four sets of simultaneous hijackings, and why Flight 93 ended up on the ground in Shanksville, PA instead of Washington DC. Airports were secure enough before; what was not secure was the instructions given to flight crews to cooperate with hijackers. Bombs on airplanes are still a risk, but for killing people, you can't beat a crop duster flying over any outdoor festival.
We have built a Maginot Line in our airports. You can be sure that the next terrorist attack will come in through the Ardennes Forest or the Low Countries. The economics virtually guarantees it.