I fly several times a year. Not quite enough to make me a 'frequent flyer', but definitely experienced.
I despise the current airport security paranoia. They are for show, not to make us safe.
1) The TSA has publicly declared they use a far higher value for the cost of one human life than we require industries to use. That is, when calculating whether to force an airline (or car) to install a safety gadget, our government values a single life at about six million dollars. If it costs eight million dollars to save one life, we don't make Boeing or Ford build or install the safety device safety device. But if it costs only five million per life saved, we require them to build and install the devices. This is called the "Value of a Statistical Life" or VSL. But the TSA state doesn't use 6 million dollars. In fact they are willing to spend more $180 million to save one life. Let me repeat, the TSA thinks it is fine to spend ONE HUNDRED EIGHTY MILLION dollars to save a life, while Ford thinks $8 million is too much. (Source for TSA value). The airlines and car companies number is much closer to that used by other government agencies. Obama's EPA values life at about 9.3 million, while the Consumer Product Safety Commission values it at a low of five million.: source. When the GOP talks about federal regulations forcing businesses to put in ridiculous safety features - this is what they mean. Consider what would happen if we did the same to the car industry. We get about 42,643 (source) fatal car crashes in the US during 2005. Using a generous 9 million per death, would be $383 billion , divided by the 62 million cars (source), comes to about $6,177. So if we raised the car safety number 50%, that's how much a new car should pay for all safety features (brakes, seat belts, airbags, bumpers, brake lights, etc.). If instead of 9 million, we used the 180 million figure the TSA uses, that would mean spending an additional $117,363 on safety. Cripes, for that amount of money we could hire everyone a chauffeur.
2) They kill people. Yes, the back scatter devices, if they are properly operated, are safer than medical and dental x rays. But did you ever notice how the dentist covers your body with LEAD? And leaves the room? Recent reports estimate that full use of the machines will cause 6-100 cancers a year. (source) In the last ten years, there have been exactly none, zero, zilch, nada, nil, terrorists deaths on airplanes leaving a US airport. OK, that doesn't include 2001, so lets make it 20 years. Then we get 3,000 for 2001, and ...none, zilch, zero more. That works out to 150 deaths a year. Over the last 30 years we get another 270 deaths on the Lockerbie flight from London to New York (so no US screening, just British, but lets count it anyway), and that's it (there were some minimal - less than 1,000 - americans killed in flights between European countries, but my cancer death rates are just for America, so they can't be included for a fair comparison.) (source). OK, so over the past 30 years, that comes to 109 deaths per year, almost all of them on a single flight that did not involve anything more dangerous than box cutters.
3) They don't catch terrorists. Not once has any machine - not the metal detectors, not the back scatter machines ever caught a real terrorist. (Yes, they routinely find weapons - most of which belong to citizens with gun licenses forgetting to check their bag. Rarely do they arrest the person - usually the worst they do is confiscate the weapon - more often they simply check it. Note, these are metal weapons that are detectable by a metal detector, you don't need an xray machine to find them.) But of the two the foiled terrorist attacks involving airplanes, one was stopped by Saudi spies, another was stopped by the passengers and stewardesses on the plane, that is it. For all the shampoo, nail clippers, snowglobes, etc. confiscated they have confiscated not a single bomb at the gates. Most importantly, the easiest way to blow up a plane is to fire a missile at it, and the machines can not stop that.
4) The majority of the deaths were caused by terrorists getting into the cockpit, not by letting people bring liquids or weapons on the plane. A solid door, lockable door would have stopped 90% of worldwide deaths. Replacing the door with a wall so that the only way into the cockpit is via an external door accessible only on the ground would be even better. This would cost less than the back scatter devices cost.
The machines are way too expensive. They kill more than they save. They don't catch terrorists. There are cheaper ways to prevent hijackings. They are an invasion of privacy. They cause a small number of cancers.
The various x ray machines are illegal under the Constitution of the US. They are offensive to the very heart and soul of our country. The only people that think they are worthwhile are either A) spendthrift, paranoid and ignorant, B) own stock in companies that make the devices, or C) Politicians trying desperately to LOOK like they are doing something against terrorism.