Eventually what you describe will force some density...if you look at an map of the Bay Area, you will see that most cities are bordered by county-owned open sp

Eventually what you describe will force some density...if you look at an map of the Bay Area, you will see that most cities are bordered by county-owned open space or parks of some kind, which creates a natural border for development. It was very forward-thinking of local governments to create these parks and open spaces back when the there was no demand for the land.