Perspective (UPDATED)

James Joyner has makes some very good points in these two posts:

Keep Calm and Carry On

While these attacks are thankfully rare, I can’t for the life of me figure out why. The Boston Marathon and the Super Bowl are comparatively easy to secure, because they’re one-offs, generate sufficient revenue to make a security investment reasonable, and obvious targets. It’s simply impossible to protect all of our schools, shopping malls, movie theaters, airports, and other places where hundreds and even thousands of people gather on a daily basis.

Why Terrorist Attacks Are So Rare

This credits government action in preventing crazies from getting the necessary materials rather than a lack of crazies. And that’s a completely plausible explanation for a relative decline in these attempts since 9/11 and OKC. But it’s noteworthy that, even before those attacks, they were pretty rare. Which leads me to think that there just aren’t that many people who simultaneously harbor a strong desire to kill large numbers of their fellow man and possess the skills to actually carry out the act.

Joyner, I think, gets to the heart of the issue here:

Unless you’re awfully good at it–in which case your results can be spectacular–you’re less likely to kill a lot of people with explosives than with a surprise gun attack.

The difference between the typical surprise gun attack and the perpetrator in Boston, is that the typical rampage killer dies in his attack while the bomber in yesterday's attack clearly wanted to live. So i would extend Joyner's point and say that in America we fortunate because there are very few people who simultaneously harbor a strong desire to kill large numbers of their fellow man and possess the skills to actually carry out the act AND ARE WILLING TO DIE IN ORDER TO KILL.

UPDATE

Megan McArdle:

And thankfully, there are not nearly as many lunatics as there are schools, or malls, or even marathons. That's why most of our public spaces are safe from mad bombers--and I'm glad to say, why they will remain so.