I think part of it has to do with just how many people here are transplants - whereas in Seattle it seemed like (at least for a 20-something recent grad living on Capitol Hill circa 2009) there was a firm social division between transplants and locals. This may have changed in the years since, considering how many more transplants there are now.
There were a few transplant circles I ran in (including a hacker space I liked a lot), but most of them being tech-centric it felt restrictive. I'd be very happy to learn if the situation has changed.
I felt similarly about San Francisco - the circles that seemed accepting of transplants (worse, techie transplants) tended to be tech-heavy, and it became impossible to "get away" from tech even during my off hours. More diverse interests tended to look at us warily - though I don't really begrudge them, there are a lot of good reasons.
I dunno, I've heard this, but having lived in the Bay Area, NYC, and the Northwest (Portland, specifically), and not being a native of any, I found the Northwest to be by far the most welcoming. There was a strong sense of community in the neighborhood (people would get together for dinners and stuff), everyone was super chill, you could get to know the regulars at coffee shops, etc. California in general seems way more cliquish.