If there were a hedge fund manager hall of fame, Ken Griffin would be a no-brainer inductee. His skillful leadership of Citadel made it one of the most successful hedge funds ever. It also made Griffin one of the wealthiest people in the world, with a net worth of nearly $37 billion. Understandably, many investors pay close attention to the stocks Griffin buys and sells. Are income investors in this group? There's a good argument that they should be. The billionaire just loaded up on one high-yield dividend stock.