Same thing around The Capitol in D.C. However, I've secretly always wondered how many of these guys are informants.
Last summer I was in the food court in Pentagon Centre and saw this bearded guy who looked Middle Eastern with a video camera methodically filming the food court. He walked all the way around, then stood in the center and slowly panned up to the third floor, lingering on the escalator area. It entirely creeped me out, especially since it is forbidden to film or take pictures in that mall. I tried to find a security guard but had no luck. When I got home I called the security office at the mall to report what I'd seen, and was greeted with a ho-hum. I haven't been back since, although it's close to where I live, except to go to Nordstrom's at the other end of the mall. I still think they are planning something for this location, across Army-Navy Drive from the Pentagon itself.