David Brin is an SF writer that I read. Here is is take on yesterdays bombing:

It is mid-April. Perforce, whatever terrorist acts we see this time of year are not presumed to be perpetrated by overseas religious fanatics. Oh, sure, our agents and satellites are scurrying about, sniffing in those directions for clues and signs, as well some of them should. Still, I’ll wager that the core of investigative attention is being paid to our home-grown monsters. Angry men whose fixations, hallucinations, grievances and heroes revolve around this week. Tax Day. Waco and Timothy McVeigh’s murderous bombing in Oklahoma City. Hitler’s Birthday. Columbine, the Virginia Tech Massacre. And warped interpretation of the Patriots’ Day anniversary of Lexington and Concord.

If you have a crazy uncle or former roommate who mutters horrid fantasies, keep a special eye open during early April, from now on. In this coming era, our paid protectors will not suffice. As I portray in EXISTENCE, we will all be (in the far truer spirit of 1776) citizen soldiers, using our cell-phone cameras and networks and noses and instincts to help protect America and civilization from lunatics. Whether it is North Koreans smuggling in a dirty bomb or your cousin waging war against his own nation, we will be the front line.

Get used to it.