The top five US public companies are Apple, Google, facebook, Microsoft, and Amazon. Three of them are HQ'd here. Netflix isn't top-5 by market cap but I wouldn't be surprised if it gets there before long, maybe displacing Microsoft.

You can certainly make that argument but it's on a whole different level now. Apple is earning 60-80 billion in profit per quarter. Many of the companies you list don't even have market caps that high.

Yes, business existed in San Francisco prior to 2012.

This latest housing crisis began in 2012.