In my opinion, urbanization in the 20th century has reduced the sense of community in large urban areas. We don’t know our neighbors (and neighborhoods?) anymore. It actually has become awkward to introduce ourselves to our neighbors. But, as Man is really a gregarious creature (we like to live in “tribes”), I’m a firm believer that the local social web will, in the future, help re-build the social tissue in large cities. These new web tools will allow us to maintain a basic privacy layer while removing some of the awkwardness in the system.
I agree with the diagnosis, but I’m not as certain with the prescribed cure. Front Porch Forum is one effort working on a solution.