I went to DC a year and a half ago, place looks like something out of that dysfunctional-future Schwarzenegger movie "The Running Man." Had the steps of the Capitol building blocked off with fencing, bodybuilder security guards with rifles on the balconies. There wasn't a specific threat; it was business as usual, post-9/11.
My british guests asked one of the guards about it, he was polite, but basically he was like "everyone is a threat these days, the Capitol could be attacked at any minute, yadda yadda."
You know, people joke about survivalists wishing for a Red Dawn scenario to come true. Sometimes, I think government has their own SHTF daydreams in which they impose martial law and boss everyone around. Sadly, since 9/11, they are a helluva lot closer to implementing their daydream than the wannabe-Wolverines.
Sorry, rant off, and the above is not intended to be cop-bashing so please don't take it that way.