Jay-Z is not his agent. Jay-Z is forming a partnership with Creative Artists Agency (CAA), which is already one of the biggest and most famous agencies around.
They represent Ryan Braun, Derek Jeter, Jason Bay, Andre Ethier, Matt Garza, Adam Jones, Carlos Quentin, Ryan Howard, Buster Posey, Roy Halladay, Ryan Zimmerman, amongst many other big names, and that's just baseball.
In sports, they also represent other big names like Dwyane Wade, Carmelo Anthony, Cristiano Ronaldo, Sidney Crosby, Tony Romo, Shaun White.
Then, in film, they represent Jennifer Aniston, James Cameron, Drew Barrymore, George Clooney, Tom Cruise, Robert Downey, Cameron Diaz, Will Ferrell, Jamie Foxx, Tom Hanks, Scarlett Johansson, Anne Hathaway, Natalie Portman, Arnold Schwarzenegger, Will Smith, Steven Spielberg, and Bruce Willis.
And in music, AC/DC, Christina Aguilera, Chris Brown, Mariah Carey, Kelly Clarkson, Green Day, John Legend, Ludacris, John Mayer, Shakira, Bruce Springsteen, Justin Timberlake, Sting, and Kanye West
It can be argued that this was actually a very smart move on his part.