Natan Gesher sent me the following email after reading my post about why flaking is so widespread in San Francisco, and I thought you all might find it interesting too:

I saw your blog posts about flaking and wanted to share something I've observed from moving around a bit (four years in Manhattan for university, then two years in Jerusalem, five years in Tel Aviv, two years in San Francisco, three and a half years in Manhattan, one year in Seattle and finally the past two+ years in Manhattan): topography seems to have an effect on how people meet each other, make friends and form friend groups.

Specifically, in cities with a lot of hills (in my experience Jerusalem, San Francisco and Seattle), neighborhood identities tend to be stronger, it's more difficult to meet new people who don't live in one's own neighborhood and therefore it becomes more important to move to the neighborhood that matches the identity one has (or wants), and friend networks within neighborhoods tend to be more stable. This could be considered "cliquey."

In flat cities (in my experience, Manhattan x3 and Tel Aviv), however, neighborhoods are more fluid, it's easier to meet new people from every neighborhood in any neighborhood and therefore it becomes less important to live in a specific neighborhood than to be within strategic commuting distance of everywhere / wherever interesting things are happening, and friend networks turn over more rapidly. This could be considered "transient."

I've hypothesized that hills within a city may impose a certain psychological barrier - despite the physical barriers that are so easy to overcome with modern forms of transportation - preventing people from wanting to transcend them, and that neighborhood cultures in hilly cities persist longer over decades and absorb new members more thoroughly.

For me, living in the lower Haight was the only time in my life that I seriously considered buying an automobile of any kind, a Vespa scooter. In retrospect, though it would have helped my commute, I don't think it would have made any difference for me socially, because the barrier that the hills represent is cultural and psychological, not really geographical.

Dan Wang and Brian Lui also had some interesting reflections on that same post, which you can find here.