What exactly are the density restrictions on residential buildings in San Francisco? I'm slightly familiar with DC and Philadelphia and in neither case is building height or zoning the key issue. Unions and crime figure in.

I'm rather against high-rise residential construction. Big buildings are fine for hotels, but for homes it leads to really shitty residential neighborhoods where people can't recognize their neighbors. I'm all in favor of three story limits. Just make thin row homes. God forbid people actually have to deal with neighbors and maintain sidewalks and so-forth. Maybe some people actually do like checking in and out of their concrete cell block on floor 50.