After five years as king of the HBO castle, CEO Bill Nelson has announced he's leaving the company to retire at the end of the year. During Nelson's near 30-year career, he bounced through a string of corporate roles before becoming top dog in 2007, subsequently overseeing the launch of the digital service HBO Go. While it might be impossible to replace such a commanding moustache, we're sure current co-President Richard Plepler will do a fine job when he takes the helm. He's responsible (in part) for bringing shows like