Past Silicon Valley property booms started in Palo Alto, adjacent to the Stanford campus, and Cupertino, home of Apple Inc., because of those institutional links and their coveted public schools, said Stephen Levy, director of the Center for Continuing Study of the California Economy in Palo Alto.

"We're a happening place because of the university and a lot of the folks that have been buying are relatively young," said Levy, who has viewed downtown condominiums selling for double what he paid in 2005. "We have the best train service to San Francisco. I can be downtown in 35 minutes."

Sean Scott, head of sales for Redwood City-based software firm Ingenuity Systems Inc., looked at a four-bedroom, two-bath home in Palo Alto last month priced at $1.8 million. The house has "soaring ceilings and generous living spaces," two patios and a "lush backyard garden," according to a marketing flyer.

20% Above Asking

A sale is pending for more than 20 percent above the asking price, or at least $2.2 million, after five bids were received, said Denise Simons, the listing agent at Alain Pinel Realtors.

"The market seems to be returning to the crazy days and the question is whether or not it is a false recovery or a sustained recovery," Scott said in an e-mail after viewing two more homes at $1.25 million or more, and declining to make any offers. "I suspect that it is a sustained recovery, given the planned liquidity events with social-networking companies."

Speculation that Facebook will go public in the next year is mounting even as the world's largest social-media site remains silent about its plans. The company may have an IPO in the first quarter of 2012 with a valuation as high as $100 billion, cable channel CNBC reported June 13, citing people familiar with the matter.

Private Share Sales

Some investors have already cashed in equity in their companies through private share sales, boosting Silicon Valley housing demand and contributing to price gains, Rosen said. Stakes in closely held firms can be sold on secondary exchanges such as SharesPost Inc., which connects buyers and sellers. The exchange values Facebook at almost $53 billion.

Shares granted to employees of public companies can't be sold until 180 days after the IPO, under U.S. securities rules.