I have an idea, let me post it and see if anyone is interested..
What about a mod for Smf Forums, DC forum in particular,
which generated a kind of view like this city thing, EXCEPT:
the forum user name is the name of the building
the size of the building = # of posts
geographic location = either geographic location as configured in signup OR alternatively, maybe draw the city as if you are drawing concentric circles, where user #1 is at center, and then the circle goes farther from the city center as member id#s increase. OR you could use the same concentric circle idea except use # of posts to determine how close to center of city they are.
you could include only people with more than a few posts to keep it from getting too busy.
Anyone want to try to make it?
you could ignore the SMF mod aspect of it for now -- just make a general purpose php (or whatever) pretty city generation service, and worry about querying a list of users,userid#,postcount values later.