The toughest CEO jobs in America

Steve Ballmer was not exactly the most well-liked CEO in history: Microsoft's (MSFT) stock shot up when he announced his retirement. No one expects the top job to be a cakewalk for Satya Nadella, but Microsoft happens to be one of the most profitable companies on the planet. It also doesn't hurt that that the Microsoft division Nadella had controlled before becoming CEO is the company's fastest growing unit.