Joe Plumeri, chairman and CEO of the Willis Group and a 1966 William & Mary graduate, built his entire 2011 commencement address around a single, provocative metaphor: play in traffic. From the Founding Fathers in Williamsburg to Tank Man in Tiananmen Square to a Google executive in Cairo, he argued that what united history's change-makers was the collective courage to defy tradition and throw themselves into the arena. He illustrated this with his own story of accidentally walking into a brokerage firm thinking it was a law firm, telling Sandy Weill, 'I don't know what you do here, but I'll bet I can do it.' Twenty years later, the kid whose head was used as a speed bag became president of Shearson Lehman Brothers.