Chris DeWolfe will hand over his CEO title at MySpace, whose growth has stagnated over the past year while the popularity of rival Facebook booms.
In addition, President Tom Anderson is in discussions to take "a new role" in MySpace, parent company News Corp. announced Wednesday.
News Corp. didn't announce a replacement for DeWolfe, who will remain on the board of MySpace China and act as a strategic advisor to the company.
The announcements come weeks after News Corp. tapped former AOL CEO Jonathan Miller to lead the unit in charge of its Web properties, including MySpace, as the chairman and CEO of News Corp.'s Digital Media Group, as well the company's chief digital officer.
MySpace, once by far the largest social-networking site in the world, has seen its popularity cool off, while Facebook's user base grows at a frenetic pace.
In March 2008, the Fox Interactive Media sites, including MySpace, had 88.3 million U.S. unique visitors, a figure that dropped to 85.1 million last month, according to comScore. In that same time period, Facebook's U.S. unique visitors grew from 36 million to 61.2 million.
Globally, Facebook sped past MySpace last year. In December, Facebook attracted 108.3 million unique visitors worldwide, while MySpace had 81 million, according to Nielsen Online.
Between December 2007 and December 2008, time spent by users on Facebook exploded by 566 percent, from 3.1 billion minutes to 20.5 billion minutes, Nielsen Online said in a Nielsen report (PDF) released last month. With this user engagement, Facebook had the highest average time per person - 3 hours and 10 minutes - of the 75 most popular online brands worldwide, according to Nielsen Online.
Experts attribute Facebook's popularity rise to several factors, including its appeal to a broader scope of people thanks to what many perceive as a more organized and controlled environment. For example, most Facebook members use their real names, which isn't the case with MySpace, and Facebook's layout is more streamlined and clean.
Facebook also offers very granular privacy controls, giving members many options to fine-tune access to their profiles and data. In addition, Facebook was first out of the gate with opening its site to applications from external developers, a move that has helped to increase its attractiveness to users.
Facebook recently announced it had reached 200 million monthly users. News Corp. said Wednesday that MySpace has 130 million "passionate followers" worldwide and 1,600 employees.
Miller plans to announce a new management structure for MySpace "in the near future," the company said.