-By Brian Morrissey

NEW YORK Mark Kingdon, CEO of Omnicom Group digital agency Organic, is leaving the shop to take the post of chief executive at Linden Lab, the company behind the virtual world Second Life.

Kingdon led Organic for seven years since taking over from agency founder Jonathan Nelson in 2001. The shop plans to begin a search for his successor immediately. Chuck Russo, Organic's chief development officer, CFO Marita Scarfi and Nelson will serve on a steering committee until a new chief executive is named.

Kingdon led Organic in rebuilding its business following the dot-com crash in 2001. He helped navigate its integration within Omnicom following its steep stock decline, solidified its standing with longtime client Chrysler and attracted Bank of America and other key clients.

Omnicom has loosely aligned Organic with BBDO, but it also works with other Omnicom shops, as well as agencies from other holding companies. It has become known for its persona-based development of Web experiences.

Kingdon today informed Organic's 25 top executives, gathered in San Francisco for a meeting, of his decision to leave.

"Everyone wishes him well," said Chad Stoller, executive director of Organic's emerging platforms group, which Kingdon formed in June 2006. "The only disappointment people have is he won't be the CEO anymore. Everyone understands it's a great opportunity at Linden."

Kingdon joined Organic from the consulting world, having worked at new business incubator Idealab following a stretch at PricewaterhouseCoopers, where he led the retail and distribution practice.

At Linden, Kingdon will inherit a company that is trying to deliver on its initial promise of creating a virtual world for the masses that could change how people interact. After a spate of initial enthusiasm among marketers for five-year-old Second Life, it has come to be seen by many as overhyped, because it has failed to move beyond the early adopter crowd. Second Life boasts 13 million "residents," although only a fraction visit regularly. According to Linden, 414,000 were logged on over the past week.

Philip Rosedale, founder of Linden, stepped aside as CEO in March. Kingdon will report to Rosedale, who remains chairman of the company.

"His management style, unwavering leadership in the face of great challenges, and approach to team-building exactly matches Linden's needs," Rosedale said in a statement. "He is a passionate believer in the potential of virtual worlds to change the world, and I look forward to working by his side while we watch it happen."