Even though I've lived in the Los Angeles area far longer than my collective time in DC, I feel like I know DC much better and even have a tighter network of people that I can just run into on the street here. Just yesterday, I ran into one of my college friends in the dining room of a Congressional Office Building, one of my young democrat friends outside my office building, and a law school friend at the Nationals stadium. 3 different run-ins from 3 different spheres of my life all in one day.
I actually think that the reason why DC feels like a small place is because it is actually small, geographically. The district is only 68 square miles. Also, most people and places that I associate with are contained in the Northwest quadrant, making it even smaller.
Funny how I can move across the country and feel more familiar and have a greater comfort zone than I do in LA. But I'm sure wherever I "settle," I'll gain a sense of direction and run into people I know.