See the second link:

Meanwhile, San Francisco—one of the most expensive cities in the United States—added just 418 new housing units in 2011, the fewest since 1993. What’s more, 149 existing units were removed, leading to a nearly nonexistent increase in housing supply.

Farther south in Menlo Park, Facebook raised billions of dollars in an IPO, instantly putting millions of dollars in the hands of early employees and investors. But as Trulia’s economist Jed Kolko notes, the surge of cash will create losers, by bidding up the cost of local housing. “If Facebook were in Texas or North Carolina,” he observes, “developers would have been building new homes in anticipation of this day,” but in Silicon Valley—as in San Francisco and Marin County farther north—it’s essentially impossible for new construction to meet rising demand for living space. So some of the people living in the area who didn’t just reap a financial windfall are poised to be priced out of their homes as high rents get even higher.

Silicon Valley has largely become zero-sum, population-wise (see also Edward Glaeser's The Triumph of the City on this subject).