Nokia (NYSE: NOK) is losing a key executive in its nascent mobile advertising unit: Mike Baker, the former CEO of Enpocket (which Nokia bought last year) and current VP and head of Nokia Interactive Advertising, is leaving the company. August 8 is his final day, reports Clickz. Baker said he wanted to go back to entrepreneurial life..he joined Enpocket back in 2004. In the year since the Enpocket acquisition, Nokia has been rolling out its mobile ad network, and has expanded it in Europe, U.S. and other parts of Asia.

Nokia has named a new head of its ad unit: Longtime Nokia exec Tom Henricksson will replace Baker. As for what’s next for Baker: “I’ve long been a personal investor in companies in the space. I’m going to do a little bit of consulting, and do some investing. That will keep me busy for a bit anyhow,” Baker told ClickZ.

• Nokia Does Another Buy: Mobile Marketing Company Enpocket