[scurvy]

I've known maybe 20% of my neighbors in SF,and I didn't live in high rises. I've lived in the low density housing you speak of. Sunset, Tenderloin, Nob Hill, and Russian Hill. People in the Sunset live very insular lives. Maybe it has to do with the immigrant nature of it, or maybe because some places are brothels or grow houses. Tenderloin had a better sense of community, and it's probably the highest density of all four places.