At least one good thing resulted from the Christmas Day incident when would-be bomber Umar Farouk Abdulmutallab tried to blow up Northwest Airlines Flight 253 into Detroit. Finally, the phrase “security theater” has made its way into the public lexicon to describe the billions of dollars governments have spent slamming barn doors shut after the livestock have left the premises.

Although the language is relatively new, frequent flyers have been having quiet conversations about security theater for nearly a decade. I’m sure you’ve had them, too: After the September 11 attacks, security authorities understood that aircraft could be turned into weapons of mass murder. Shoe-bomber Richard Reid drove security authorities to x-ray our footwear. A plot hatched in the United Kingdom in 2006 focused their attention on liquid explosives.

In each case, it made good sense to take action against a known risk, but the official response begged the question: If would-be terrorists know that you’re ready for them, why would they try it again?

We have to hope that less-visible security measures are in place to deal with threats that aren’t quite as predictable. But meanwhile, the nagging suspicion is that the public is the primary audience for the shoe checks, the guidelines for liquids, and even the full-body scanners that former secretary of the U.S. Department of Homeland Security Michael Chertoff has been hawking on behalf of a consulting client. Even if they do little or nothing to make us safer, the extra checks might make some travelers a bit less nervous.

In late December, The New York Times cited outside critics who found the government “too quick to rely on technology that may calm the public, but that terrorists can quickly outsmart.” According to Andrew R. Thomas, editor of the Journal of Transportation Security, “it’s not just the billions of dollars, but the billions of hours people have spent in airports that have been wasted.”

After all that, it was prompt action by several passengers, not a multi-gajillion-dollar security network, that stopped the Christmas bomber. And on January 23, when a deranged passenger tried to break into the cockpit on a flight from Washington, D.C., to Las Vegas, his seatmates intervened.

None of us wants to be on the flight where passengers have to defend their own safety in mid-air. If I survived the experience, I’m sure I’d never fly again. But it’s a calculated gamble that each of us accepts every time we board a plane. While the risk is vanishingly small, in the range of one attack per millions of flights, it’s greater than zero.

But maybe that’s the 21st century trade-off. If we acknowledge that unspeakably bad things will happen very infrequently despite best efforts, the terrorists win a small psychological victory but lose much of their ability to terrify. If we don’t, security theater becomes ever more expensive and intrusive, for little or no gain. If absolute safety is a costly illusion, it may be that a dose of realism is our best defense.

Mitchell Beer, CMM, is president and CEO of The Conference Publishers Inc., one of the world’s leading specialists in capturing and repurposing conference content. Beer blogs at http://theconferencepublishers.com/blog. Send comments, facts, arguments, or column ideas to mitchell@theconferencepublishers.com.