Exclusive: Yahoo's David Ko to Head Mobile at Online Gaming Powerhouse Zynga

David Ko (pictured here), who just announced he was leaving Yahoo as head of its powerful U.S. Audience unit, is taking a job heading mobile efforts at hot social gaming start-up Zynga, according to sources.

The move comes only a day after Jimmy Pitaro, who also departed his job as SVP of Media at the Internet giant last week (working under Ko, in fact), landed at Disney (DIS) as the new co-president of its Internet division.

For Zynga–the fast-growing San Francisco-based maker of such online hits as Farmville and Mafia Wars that got its start on Facebook–mobile is becoming a critical new platform for growth, as consumers use a variety of increasingly functional mobile devices, such as smartphones and tablet computers.

It’s also the fastest growing area internationally, where mobile phones are more widespread and where Zynga is seeking its next spurt of growth.

Sources said Zynga had been pursuing Ko for months.

Before heading the Audience unit at Yahoo (YHOO), Ko ran its mobile operations, which included heading product development, making distribution deals and more.

Under Ko, Yahoo’s mobile efforts first centered on building apps for smartphones, such as the Apple (AAPL) iPhone, but shifted to encompass more of its copious content assets.

Ko, who worked in a variety of areas at Yahoo, took over as SVP of Yahoo Mobile in 2009 after Marco Boerries left as EVP of the Connected Device Division, which now does not exist under that name.

Ko had also run Yahoo’s mobile business in the Asia-Pacific region.

According to one of Ko’s old Yahoo bios, he previously worked at Salomon Smith Barney as a senior associate and analyst. He is a graduate of New York University’s Stern School of Business.

Ko, who lives in San Francisco with his family, the bio notes, inexplicably “enjoys reading tech blogs.”

In his new job, as SVP of Mobile at Zynga, he will report directly to CEO Mark Pincus, sources said.