Think about adding a social aspect. "Following" cities for example and having a feed with updates (a la Github) of the stuff you follow. This way you will add user-to-user interaction and will help you with surfacing good content.
I sincerely wish we had had the foresight to explore this further. Early "homesteaders" of GeoCities would select their URL based on a loose ontology of (neighbor)"hoods" and (sub)"burbs" (a fashion oriented page might be hosted at /FashionAvenue/Catwalk/1493). While this certainly made scaling the backend easy, it also created a sense of community (keeping an eye on your "neighbors", the mad rush to get a site with a hot address (/1000) when a new burb would open).
The need to provide a simple path for all of Yahoo!'s users led to the now familiar "/username", but I'm not entirely certain it was for the better.
( I recall one conversation where we considered providing the ability to tag derelict homesteads with virtual spray paint )
