Yahoo’s head of U.S. Audience unit, David Ko, who just announced that he is leaving Yahoo, assumes a position in heading mobile efforts at social gaming startup Zynga. According to sources, Zynga has been pursuing Ko for months.  SVP of Media Jimmy Pitaro also left his job at the tech giant last week and is now Disney’s co-President of internet division.  Kara Swisher has the details, citing

“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.”

San Francisco-based startup Zynga is the creator of Farmville and Mafia Wars, which debuted on Facebook. With the increasing popularity of mobile devices such as smartphones and tablets, even cutting netbooks sales by half, the mobile industry is skyrocketing, and is in fact the fastest-growing area internationally. As Zynga’s new SVP of Mobile, Ko will directly report to CEO Mark Pincus.

Ko is not new to the mobile industry, running Yahoo’s mobile operations prior to being the head of US Audience unit. He headed product development, distribution deals and such. He was also SVP of Yahoo’s Mobile last 2009 prior to Marco Boerries resignation as EVP of Connected Device Division.  Ko is also responsible for Yahoo’s mobile business in Asia-Pacific; a region where social and mobile gaming is already quite popular.

Zynga’s been making a few moves of its own lately, gaining employees and opening new offices across the globe.  Zynga’s taking a platform approach to gaming, which requires a number of partners and a deep support system for clients, advertisers and developers.  Zynga has a heavy presence on Facebook, and once held a more involved partnership with Yahoo’s game portal.  With Zynga’s success on the iPhone, mobile gaming is also of great interest to the company.