On the other hand, all this "security" does force bad people to work a little harder to bypass it. And that extra work means more chances to foil plots before they hatch. Someone mentioned the possibility of combining many small containers of liquid explosive into a larger bomb. Which would probably work if they all made it through. But it would require several conspirators instead of a single one, leading to several more ways for the plan to fall apart, hopefully before it even got to the airport.