Kara Swisher had it about an hour before it was announced:

While did-he-walk-or-was-he-pushed speculation will no doubt be rampant, sources said Yang has and will play an important role in the search for his replacement.

Sources close to the board expect the choice will end up being an outsider and likely not current Yahoo President Sue Decker, although she is being considered for the job.

But both she and Yang have been closely affiliated with each other, as the company has struggled to right itself after tumultuous year and its stock price has plummeted.

Among the tumults, management missteps, a hostile takeover attempt by Microsoft, and a proxy fight by activist shareholder Carl Icahn. Yahoo’s search and ad businesses have declined in the midst of the current economic meltdown. Yang will return to his former role as “Chief Yahoo.”

According to sources, both Yang and the board have been discussing the move for months, although publicly Yang has been saying he was going to stay in place to see through the many changes he has made in his 16-month tenure.

Kara followed quickly with the entire memo from Jerry Yang to employees at Yahoo about his plans to step down. TechCrunch chimes in with the Yahoo press release; and some speculation on who will be next. Finally, the Yahoo conducting Search for New CEO release comes via Techmeme.