Zynga CEO Mark Pincus is still majority owner but has stepped aside as boss in favor of Don Mattrick, former chief of Microsoft's Xbox division. Mattrick joins the struggling social-gaming giant with a reputation as an unsung visionary, but it's unclear whether his management expertise will be enough. "Pincus is still the chief product officer. So the question is, what's actually changed day to day in terms of making hit games?" asks industry analyst Richard Greenfield.