[barce]

I'd say that factual thing to focus on is density of people. If you apply Metcalfe's law to IRL connections of people you just meet out and about, it's very appealing for those working on a startup and being stuck on a problem. You very often accidentally run into people in SF that can either help with that problem, or fund you so that you can work on it longer. Just this afternoon at an SF Museum, I ran into 2 investors with a net worth both north of $50 million. This simply hasn't happened in the East Bay (more middle class than wealthy people), nor down the Peninsula (not dense enough).