Don Mattrick, who oversees Microsoft's gaming business as president of its "Interactive Entertainment Business," is leaving the company to helm social gaming company Zynga. Mark Pincus relinquishes the title. Reports first appearing on All Things D were just confirmed to Fast Company by Zynga. The online social gaming platform has had a rough year, with massive layoffs, office closures, and revenue dips. Microsoft reportedly doesn't have a replacement lined up for Mattrick, who joined the company in 2007.