It's an idea that's been batted around by the TSA and airport security for at least five years now: Why don't airports get shoe scanners to eliminate passengers having to take off their shoes at security? And in those five years, despite brief testing periods at airports like LAX and TLV, not one airport has stepped up to buy a slew of the machines and make shoe scanning mandatory. Why? Because it won't make a difference in the long run. And here's why:

· It's something full-body scanners should take care of

The words on everyone's lips these days, post-Christmas crotch bomber, are "Full-Body Scanning," and thus we're not surprised that the argument for separate shoe scanners is back. But if a full-body scanner is doing its job of scanning your full body, why would we need shoe scanners? Well, if you look at one of the machines, you'll see that the scanning doesn't go down to the floor. Perhaps they should just add a special attachment that does, so that airports aren't spending millions more dollars buying new machines and making space for those.