After making an estimated $200 to $400 million for themselves and investors by selling their start-up in-game ad network to Microsoft last year, the founders of Massive have decided to leave the company.

　　CEO Mitchell Davis and the company's president of new media Nicholas Longano will depart Massive at the end of January. Microsoft, which bought the firm in April, has put a 12-year business development veteran in charge of the operation. Cory Van Arsdale, who currently oversees business development and partnerships for the MSN and the Online Services Group, will assume day-to-day operational responsibilities for Massive, according to the company.

　　In a statement, Davis said, "Pursuing entrepreneurial start-ups has been my passion. Massive is well-positioned in the in-game advertising industry, and I look forward to watching its future growth from outside the company as I move on to pursue new interests outside of Massive and Microsoft. I wish Cory and the team all the best as they go forward."

　　Massive was one of the early movers in the still-maturing in-game ad space and counts Sony Online Entertainment, 2K Games, and THQ among its clients.