"In the entrepreneurial spirit that Forbes has always championed, Jim will be setting up his own media management company," Steve Forbes, president and CEO of Forbes, said in an internal memo released to employees on Thursday.

Quoted in the memo, Spanfeller said: "The world of media has changed rapidly in the past 10 years and the velocity of the change promises only to increase going forward," adding: "Now I see a huge opportunity to have my own media management business that will help other traditional media companies make the most of their enormous prospects in digital venues."

During his tenure, Spanfeller has overseen the development of Forbes Digital, which includes Forbes.com, ForbesTraveler.com, Investopedia.com, RealClearPolitics.com, RealClearMarkets.com, Real Clear Sports, and Forbes Business and Finance Blog Network, which together reach 40 million unique visitors a month.

At present, Forbes.com has 18 million unique visitors a month. Spanfeller will to stay on through a transition period at least through Labor Day, according to Forbes.

Like many a media empire today, Forbes is in a state of flux. Upon completing the merger of its online and print editorial operations in January, it laid off 19 staffers, shuttered its auto site and severely cut the staff at Forbes Traveler. In March, Forbes announced plans to lay off another 50 employees.

In May, Roger McNamee, who helped spearhead Elevation Partners' decision to buy a 40% stake in Forbes Media about three years ago, resigned from the Forbes board. Elevation's Bret Pearlman -- known as an aggressive cost-cutter -- was tapped to replace McNamee.

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