"Remember Richard Reid, the guy who tried to light up his shoe on the airplane? After that we had to take off our shoes. Imagine what would have happened if he had hid that bomb in his pants," Boyd said.

-- Michael Boyd, president of the Boyd Group, an aviation consulting firm in Evergreen, Colorado.

The problem, as some people in this article point out, is that security restrictions that focus on potentially harmful objects can never be 100 percent. So, nobody can take toothpaste onto an airplane. So you have thousands, millions, of people dumping their toothpaste at the checkpoint. Everybody knows they can't take toothpaste on board. Normal law-abiding people diligently attempt to remember to not have toothpaste in their carry-on luggage. And then one of those law-abiding people simply forgets about the toothpaste in his back pocket, nobody notices it at the checkpoint, and he gets onto the airplane with it.

So what was the point, really, of making all those other people dump their toothpaste?

I understand the immediate restrictions -- they were a panicked reaction, based on, "we don't know the full ramifications of this plot, so we're erring on the side of caution." That makes sense, in the short term.

But there is talk of making the no liquids restriction permanent. Talk of banning cell phones, laptop computers, MP3 players. Can you imagine trusting your laptop to the ravages of checked baggage? Me neither. Although, on the plus side, a de-emphasis on carry-on might reverse a twenty-year trend of people hogging the overhead bin space.

Flights from England reportedly banned books and can you imagine the horrors if that ban became permanent? A ten hour flight without a book? And what could you do with a book, anyway? Chuck it at the back of somebody's head?

Let's face it, anybody sufficiently motivated will find a way around any security measures you can possibly devise. Ban guns? They use box cutters. Ban box cutters? They hide explosives in their shoes. Ban shoes? They hide explosives in their drinks. Ban drinks? They can hide explosives in their digestive tracts. We could make it so you can't get on a plane with anything but your body and your passport, and they will find a way to hide explosives under their nails and the trigger inside the passport. (Jeez, don't these security people watch James Bond films?)

Things that can be used as part of a terrorist plot -- once you're talking suicide bombers, anyway -- are ubiquitous and fundamentally un-bannable. The rare thing is the person who is actually planning to become a suicide bomber. And how do you prevent those people from getting on the airplane? Well, British officials already did this time, so I guess they should keep doing whatever they did.

But, as this Alternet article have suggested, the point of airport screening is not to prevent would-be terrorists from getting would-be objects of terror on board an airplane -- it is to make passengers feel that they are being protected from would-be terrorists. (Or perhaps, as MikeK suggested, it is to make sure that certain people in the TSA never have to testify before a Senate sub-committee as to why they didn't ban carry-on liquids.) Either way, they are a psychological measure only, and make no material difference in our safety.