San Francisco is the second-densest city in the country, and is one of only a few cities (and the only city in the West) that had a large urban core designed in the pre-car era, which means that its infrastructure is already designed to accomodate dense urban development moreso than any other American city west of Chicago.
Contrary to popular belief, making money in the Bay Area isn't that difficult or unlikely. I think the comparison to a gold rush is more of a meme than a representation of what's actually occurring (>95% of new arrivals are not entrepreneurs).
The good news is that tens of thousands of people from impoverished countries have been able to move here, become US citizens, and live a first-world life they might not have had access to otherwise. The sad part is, they're not cool -- or "weird" -- enough, so they have to live 90 minutes away.