All of you frequent fliers out there, you know the drill. Take off your shoes, because of Richard Reid, the "shoe bomber." Remove your hair gel from your backpack because of the bombers who targeted Heathrow using liquid hydrogen peroxide. When you get on a plane, you must also, from now on, be prepared to remove any blankets from your lap before landing -- too bad if you're asleep! -- because of the Christmas Day underwear bomber.

When someone invents a way to hide explosive powder inside a toothbrush case, prepare to remove your toothbrush. And while you're at it, throw a pinch of salt over your left shoulder as you board the plane. But never, at any moment, imagine that the rigamarole of airport security is guaranteed to make you safer -- for no one knows which of these measures, if any, is actually necessary.

Worse, no one has any financial or political incentive to find out. The fact is, since the hurried and heavily politicized creation of the Department of Homeland Security and its junior partner, the Transportation Security Administration, neither their priorities nor their spending patterns has been subject to serious scrutiny. They have never been forced to make hard choices. On the contrary, both have been encouraged by their congressional funders to spend money in reaction to every perceived new threat, real or otherwise: Thus full-body scanners, unacceptable as recently as last summer, will now be rushed into use. In just a few years -- under a Republican administration and mostly Republican Congresses -- these institutions thus grew into vast, unruly bureaucracies, some of whose activities bear only a distant relationship to public safety.

So customary has it become to repeat old, familiar lists of ludicrous public projects that readers who cannot bear to read the litany one more time might want to skip to the next paragraph. For yes, it is true: Having started with 13 employees in January 2002, the TSA now employs 60,000, and in the process of its expansion the organization found it had money for all kinds of extras. As I wrote in 2005, some $350,000 of its $6 billion budget once was spent on a gym; $500,000 was spent on artwork and silk plants, and untold millions are annually spent in overhiring, since determining when there will be long security lines at an airport has never been the sort of thing at which the federal government excels.

As for the DHS, its 2010 budget came in at $55 billion, some of which (according to the economist Veronique de Rugy, writing in 2006) will invariably be spent on things like the $63,000 decontamination unit in rural Washington, where no one was trained to use it, more biochemical suits for Grand Forks, N.D., than the town has police officers to wear them and $557,400 worth of rescue and communications equipment for some 1,500 residents of the town of North Pole, Alaska. Not to mention what is spent on the "needs" of the constituents of other important members of Congress.

It is not actually DHS or TSA employees who are at fault for these kinds of decisions. From the very beginning, security experts and even the agencies' own inspectors general have pointed to the absurdity of TSA and DHS spending patterns, many of which are driven by the latest scare story (I wish I'd been at the celebratory New Year's Eve party undoubtedly thrown by the manufacturers of those full-body scanners). And from the very beginning, Congress has fought back against critics, repeatedly allocating funds to unnecessary local projects, reacting to sensational news stories, spending money in ways that suit its members and then declaring itself shocked -- shocked! -- to discover that our multibillion-dollar homeland security apparatus was unable to stop a clearly disturbed Nigerian from boarding a Detroit-bound plane.

Imagine if the TSA's vast budget were dedicated to the creation of a cutting-edge computer network that could have made security officers in Amsterdam instantly aware of the warning from the Detroit bombing suspect's father. Imagine that, instead of relying on full-body X-ray scanners or long-haul flight-blanket deprivation, we had highly paid and trained consular officers in places such as Nigeria. Even then security would not be perfect (and I'm not sure that airborne terrorism is even the worst thing we have to worry about). But it would make sense to have a smaller, less expensive and less wasteful system. It would make sense to have a system based on real risks and priorities, instead of the stories featured on cable news. It would make sense to fight the next battle, for once, instead of the last one. "Sense," though, is not the criterion by which public money is spent in this country -- and hasn't been for a long time.

applebaumletters@washpost.com