SOMA (South of Market Area of San Francisco -- the South/East of Market Street, formerly a lot of warehouses) underwent a lot of renovation over the last 5 years as many of the new social/mobile tech companies moved in from Silicon Valley proper, in order to attract younger professionals who wanted a more urban setting for their work/personal lives.
It's something that was enabled by the current generation of software/internet/mobile startups that don't require much capital equipment or on premise IT infrastructure. It's difficult to do this running a chip startup, since you need all sorts of prototyping/testing equipment even if you are fabless.
