A San Francisco couple who made a fortune in social networking has bought a 360-acre vineyard estate overlooking Sonoma for $13.6 million.

It's one of the county's largest residential real estate deals since former Citigroup CEO Sanford Weill paid $31 million for another Sonoma estate last year.

The new owners of the Gehricke Road ranch are Michael and Xochi Birch of San Francisco, who founded Bebo.com in 2005. They sold their share of the site to AOL in 2008 for $595 million.

The estate had been listed for $19.5 million. The parties didn't disclose the sale price, which was found in county property records filed last week.

It was owned by Sonoma plastic surgeon Dr. John Emery and his wife Deborah. It includes a home, two private lakes, 30 acres of vineyards and an equestrian center.

"The views are jaw-dropping," said Linda Yenni of Blakeslee Crain & Yenni Wine Realty International, who handled the sale.

The hillside estate also boasts a winery building and hospitality center, but wines are not made there now. Emery Estate wines are produced at an offsite facility, and the Emerys' wine brand was not included in the sale.

Sales of Bay Area homes for $1 million or more grew 25 percent last year, as affluent buyers found bargains at the high end of the market, according to real estate analysts.

"It's a lot more active than people think," Yenni said.

The Emerys bought the Sonoma estate in 1994 and raised Arabian horses there. They also developed the vineyards and lakes.

Canadian-born John Emery, a 1964 Olympic gold medalist in bobsled racing, opened a cosmetic surgery practice in San Francisco in 1968.

Deborah Emery was an Oakland Raiderette cheerleader, fashion model and actress who won the California title in the Mrs. United States Pageant in 1992.

The couple moved to Sonoma in the 1980s. Since then, they've been active in Sonoma Valley causes, including the Boys & Girls Clubs of Sonoma Valley.

The Birches, who have a $29 million mansion in San Francisco's Pacific Heights neighborhood, were attracted by the estate's serene mountain setting, Yenni said.

English-born Michael Birch started several Internet companies before he and his wife founded Bebo.com in San Francisco in 2005. The social networking site grew quickly and was snapped up by AOL three years later.

But AOL failed to popularize Bebo, which was overshadowed by Facebook, Twitter and other social networking sites. AOL sold Bebo to private investors last year for less than $10 million. Its new owners redesigned the website in February.

The Birches couldn't be reached for comment.

News researcher Teresa Meikle contributed to this report.