"Terrorists want large, splashy attacks on specific sorts of targets that have high emotional resonance..."

"... for both the victims and the people on your side who you hope to recruit, or tap for money.  This helps explain why Al Qaeda was so obsessed with the Twin Towers, a place that — until they fell — most New Yorkers regarded as a rather ugly landmark containing some so-so office space.  To a terrorist group looking for publicity, on the other hand, it had immense symbolic value: the tallest building in America's biggest city, with the hubristic name of 'World Trade Center.' That's why we don't get high-frequency, low-intensity attacks on crowded spaces near some Texas town that no one in Abottabad [sic] has ever heard of.  When attacks on those places happen, they tend to be the provenance of local lunatics for whom the nearby mall, or primary school, has some immense symbolic emotional importance."

Says Megan McArdle. This reasoning suggests that if only we'd avoid prideful spectacles we could deflect the Qaeda crowd. But there will always be local lunatics, and it's impossible to avoid all the tiny targets like schools and shops that every town has....

Adam Lanza was bullied while he attended Sandy Hook Elementary and his mother Nancy considered suing the school for turning a blind eye to the abuse, an unnamed Lanza family member told the New York Daily News.

“Adam would come home with bruises all over his body,” the relative told the Daily News. “His mom would ask him what was wrong, and he wouldn’t say anything. He would just sit there.”

Know your local lunatics. And for God's sake don't torment them. Don't create them out of whatever raw material you find around. Here's a pressure cooker. What can we put in it?

Now, these local lunatics tend to show their faces. It's a showdown. They die or get captured quickly. We know who did it.

On 9/11, every building I saw seemed shockingly vulnerable. I wondered if all buildings would come down. How deceptively solid these things seem, but there are people in the world who would destroy everything anybody builds. And yet so many buildings have remained standing all these years. I didn't think it would work out this well. Terrorists in my town bombed a minor spectacle of a building 40 years ago, but since 9/11, the building have held up.

After 9/11, I obsessed about what the terrorists would do next and, naturally, I thought of the things that would hit me and the people I knew. I pictured a day when 100 suicide bombers, one by one, in 100 different college towns stepped into a crowded café or movie theater or sports event and blew up. But that never happened. McArdle's theory suggests why. That's local-lunatic level. Too lowly for the Qaeda-type brand.

But is a crowd waiting at the finish line of the Boston Marathon such a spectacle? Are crappy pressure-cooker bombs the mark of a prideful organization that once commandeered 4 jet planes and piloted 3 of them into major landmarks?

We don't yet know who the Boston bomber is or even whether it's bomber or bombers. Using McArdle's reasoning, one wonders who fixates on the Boston Marathon. Do the people in Abbottabad care about our lengthy footraces? And why target the spectators? Or was the first bomb, planted in the spectators, supposed to make the runners run toward the second bomb? That's an evil trick, but hardly anything that seen from the other side of the globe could look like glory.