Since the terrorist attacks on New York and Washington DC on September 11th 2001, Governments across the world have placed a newfound priority on domestic security. National security is no longer about something that protects our borders from outside assault; it's now intimately concerned with what happens within our country.
It makes us feel safe and comfortable to think that there's someone, somewhere in the Government who actually knows something about domestic security, and is implementing security measures with our best interests at heart.
Unfortunately, though, it's reasonably obvious that that isn't the case. Almost all of the domestic security "enhancements" which have been implemented since 2001 have very little real effect on anyone's ability to attack anything they like. Most security measures are what Bruce Schneier likes to call "Security Theatre," measures which make you think, "Well, it must be enhancing security otherwise they wouldn't make us put up with all this annoying crap!"
So we now live in a world where everyone over the age of 16 is allowed to drive a vehicle which is fueled from a petrol tank containing stored chemical energy equivalent of two sticks of Dynamite, even though sales of nitrate-based fertilizer are heavily controlled. And because most people simply swallow "security" without giving it any critical thought, very few people think about the fact that people who want to blow things up would be crashing petrol-filled cars into them instead of using explosives; And the fact that nobody is crashing petrol-filled cars into things probably means that there isn't anyone out there who wants to do it; And if there's nobody out there who wants to blow things up, why are we spending all this money to prevent it?
If we think hard about the security theatre which has been imposed on us over the last few years, we're forced to conclude that most of it is ham-fisted at best. At worst some of the "security" measures we have actually AID attackers, by sending signals about what our security institutions are actually interested in looking for, and allowing attackers to calibrate their attacks to avoid telltales which might tip-off the authorities. And we've collectively spent billions of dollars to arrive at this result. Is that expenditure wise if the magnitude of the credible threat is extremely low?
(update 21 November 2005: Commonwealth Immigration Minister Senatator Amanda Vanstone doesn't seem to think so. I almost uniformly take the opposite view to the good Senator on pretty much every issue she ever opens her mouth to talk about, but we're strangely united on this one. Go figure...)
Lets look at aviation security as an example...