The elitists came to Northern California - a vanguard of social liberalism, student protest, and most importantly communitarianism - and brought their elitism with them.
Northern California still exists in the nostalgic hippie image of the 60s, but it's compartmentalised, like the Dropbox brogrammers elbowing out kids at a playground. Public spaces increasingly become private in the name of profit.
Over time, the feel of free love will fade away entirely in the Bay Area. Everyone interesting who isn't a millionaire will be pushed to the margins, and eventually, more welcoming spaces, like Detroit. I implore the tech elite of Silicon Valley to consider a future where an expensive tech-centered monoculture makes the Bay Area an unattractive location for long-term employees, and instead relying on mercenary college grads who put up with the cost and the crazy for a few years before moving on to a more fulfilling job and place to call home.