Bruce Schneier has news of a study (by Ohio State political science professor John Mueller. Titled "The Quixotic Quest for Invulnerability: Assessing the Costs, Benefits, and Probabilities of Protecting the Homeland,") that makes complete sense and yet will never be considered, probably never even read, by those who hold the purse strings:
This paper attempts to set out some general parameters for coming to grips with a central homeland security concern: the effort to make potential targets invulnerable, or at least notably less vulnerable, to terrorist attack. It argues that protection makes sense only when protection is feasible for an entire class of potential targets and when the destruction of something in that target set would have quite large physical, economic, psychological, and/or political consequences. There are a very large number of potential targets where protection is essentially a waste of resources and a much more limited one where it may be effective.
I urge you to skim Shneier's precis and then read Mueller's paper (it's a .pdf, so all you lucky people with Kindles and Sony Readers and iPhones can download it to your spiffy device and read while you water the lawn or brush your teeth. For those with low stress/fear thresholds, I would not recommend reading while eating. The basic theme is: you can't stop terrorists. So if that's something that frightens you, just delete this now and go sit in the sun. Seriously, know yourself. Don't jack up your cortisol levels if this kind of stuff gets to you. I haven't watched TV news for a dozen years because it irritates me so much; if you choose not to read this, I understand.