In addition to San Francisco I've lived in the US South, the Northeast an in Europe. And out of all those regions I feel the Bay Area has been the most conservative and discordant. It's really a shame how a combination of the Byzantine legal processes and small cadres who know and shape the system have created a tyranny of the minority in the Bay Area and San Francisco in particular.
This same distinction also applies to the type of startup that gets founded in each place. South Bay attracts more companies that are capitalizing on a technical change in the world - Google, Apple, Netflix, hardware companies like NVidia and Memorex, drone startups, large scale enterprise software like Cloudera or Palantir. San Francisco attracts more companies that are capitalizing on a social change: AirBnB, Uber, Lyft, Stripe, Zynga, Bird, Lime, Twitter, Medium, etc. Notable exceptions are Facebook (social change but in the South Bay, though they've also built a top-notch technology org) and DropBox (technical, but in SF).
I'm genuinely curious how you are seeing Nextdoor activity outside of your own Nextdoor neighborhood, given that How Nextdoor limits participants by neighborhood and verifies addresses before you can even read postings. I can't even find an option to see other neighborhoods. As my mom was dying and I was helping to find resources and later sell her stuff, the only way I could get access was to register with her address and then wait for the coded postcard.