For several years after college, like many of our friends, the Hoos and I lived in the vicinity of our university. It helped that the school was in Washington, DC-metro area which was rich in culture and jobs, even if the housing market was crazy expensive.
When we moved up north in 2002 we were doing so for two key reasons, 1.) so the Hoos could go to law school and 2.) so we could be closer to our families. We also did so knowing that we would be leaving the community of friends we had grown into adulthood with (so to speak).
While we were moving back closer to where we had each grown up, we didn't really know many people. I still keep in touch with some friends from high school, and my best friend is still on Long Island with her family, but she is still a good three hour drive or so away. Besides, leaving high school, I was pretty confident that I wasn't really interested in seeing most of those people again...doesn't everyone say that?
Five years later the Hoos and I still have a relatively small community of local friends. Two of which are our neighbors, a married couple around our age - and they are in the process of moving. We have met a few families through LP's day care and we are slowly building friendships with them., but haven't reach the point of a weekend phone call, "Hey, we're ordering in, you guys want to come over and hang out and eat some pizza."
As you get older, I guess it is harder to meet people. For a while you can make your own friends. Then you make couple friends - which is more difficult because all four of you have to get along and be somewhat compatible. Now we either have to look for families similar to ours, or people who don't mind that we have a munchkin as our fifth wheel...