A good article by Schneier on Security.
The key to these countermeasures is to find the pattern: the common attack tactic that is worth defending against. That takes data. A single instance of an attack that didn’t work — liquid bombs, shoe bombs — or one instance that did — 9/11 — is not a pattern. Implementing defensive tactics against them is the same as my safari guide saying: “We’ve only ever heard of one tourist encountering a lion. He stared it down and survived. Another tourist tried the same thing with a leopard, and he got eaten. So when you see a lion….” The advice I was given was based on thousands of years of collective wisdom from people encountering African animals again and again.
Compare this with the Transportation Security Administration’s approach. With every unique threat, TSA implements a countermeasure with no basis to say that it helps, or that the threat will ever recur.
A bit on the long side, but worth the read.