The legendary Charles C. "Cash and Carry" Pyle, considered by most to be the first sports agent, negotiated a $3,000-per-game contract for Red Grange to play professional football for the Chicago Bears in 1933. Today, salaries in the tens of millions of dollars are commonplace, and instead of theatrical promoters and impresarios, professionally trained businessmen and lawyers dominate the business. But whereas rules and penalties govern the playing...