Shawn Corey Carter, a.k.a. Jay-Z, 36, is president and CEO of Def Jam Records. For most mortals that would be an all-engrossing position and a magnificent accomplishment. But Jay-Z is on another level. He’s also one of the owners and founders of the Roc-A-Fella empire, which includes Roc-A-Fella Records, Roc-La-Familia, Roc-A-Fella Films and Rocawear. And he owns part of the New Jersey Nets and the 40/40 Club, an upscale sports bar with locations in Manhattan and Atlantic City. It may not be trains and steel, but it’s an empire all the same. Oh, Jay-Z is also a five-time Grammy-winning recording artist, boyfriend to Beyonce and an advocate for water conservation and for the one billion people around the world who lack access to safe drinking water. Bottom line, you’ve got to have unreal powers of concentration to have that many balls in the air at one time.