I agree. And for some reason this incident got me reading the wikipedia page on the Maryland/Beltway sniper attacks. Talk about a vicious and paralyzing approach. I didn't realize that John Allen Muhammed, the older one, had "practiced" killing people out west prior to going on a full-blown shooting spree in Maryland/Virginia.
Yep, it's a good comparison except for the higher bodycount.
At essence, terrorism is probably most effective when it makes people feel unsafe in areas of their life where they normally do feel safe. Like on their front porch opening a package, or in their car (at least with regard to a sniper attack). Especially with the DC attacks, what can you do? Not drive to work?