How do you think the psychogeography of the city might be affecting identity and tribalism? Do you suspect the trend is more towards collaboration or fragmentation?
That word "psychogeography" probably means something, but guys who use it go out on Situationist drifts and look for urban ley-lines. I do a lot of similar activity, but I don't like to dignify it too much.
Modern large cities are the engines of globalization in the way that New York used to be an engine of Americanization. You look at New York back in the 1800s, obviously collaboration and fragmentation were going on there at the same time. Little Italy, Little Ukraine, whatever... but those sharp distinctions tended to melt with time. Cities that segregate their citizens into ghettos tend to go broke.