His tenure included an unsolicited acquisition attempt by Microsoft, whose failure critics blamed on Yang and the Yahoo board. Later, a deal to let Yahoo run Google search ads collapsed after it became clear the U.S. government planned to challenge it due to antitrust concerns. The deal would have given Yahoo's revenue a significant boost.

Yang's tenure as CEO also featured two big rounds of layoffs, an embarrassing exodus of high-profile managers, disappointing financial results, a tanking stock price, free-falling employee morale and little or no advances in key areas, like search usage and search advertising.

He also oversaw the launch of several ambitious technology projects designed to improve Yahoo's services for end-users, developers, publishers and advertisers. Some have been delivered and others are in progress, like Yahoo Open Strategy (YOS), a project to rearchitect the company's sites and services to tap into the popularity of social networking.

With YOS, Yahoo pledges to open all its sites, online services and Web applications to outside developers, and give users a "social profile" dashboard to unify and manage their Yahoo services.

Yang plans to remain on the Yahoo board and retain his Chief Yahoo title.