[santaclaus]

> What's to stop San Francisco from creating a lot more high-density housing?

Entrenched residents who oppose new construction, primarily. Look at the recent kerfuffles involving residents opposing the replacement of parking lots with housing.

[WillPostForFood]

Lack of infrastructure as well. Despite the low density, it is pain to get around SF and bay area generally unless you are luck enough to have a trip that starts or ends near one of the few rail lines. Double the density, and getting around would go from bad to worse.

[panic]

That's not necessarily true. More density could allow people to live closer to work and reduce the amount of traffic.

[WillPostForFood]

Even in dense cities (Manhattan), most people don't live walking distance to work. But they have a great public transportation system, so it works. The Bay Area has a terrible public transit system, and if you add density without improving it will get a lot harder to get around.

Also, the big tech jobs centers (apple/facebook/Google) are in the south bay, and many of their employees (especially those without kids) choose to live in San Francisco because it is a much more interesting vibrant interesting place than Mountain View, Menlo Park, or Cupertino. Someone living in Noe Valley and working at Apple could already live closer to work, for much less, if that's what they wanted.

So adding high density housing will allow some people to live closer, and some to live farther, but it will add incrementally more traffic. That's fine, but let's at least address the infrastructure in tandem, if not first.