The appearance of Bill Gates and Warren Buffett at the Lied Center last week was a reminder of the fluidity in American society that allows talent and drive — not birthright and connection — to earn power and wealth. Although both men came from comfortable backgrounds, neither was born to that old wealth stratum of American society that sometimes seems to be tantamount to an aristocracy. Dressed casually, they sat on a couple of stools, cracking jokes, speaking plainly, fielding unscripted questions. “They seemed like ordinary people, very normal, very knowledgeable and funny,” observed Yong Zhao, a University of Nebraska-Lincoln...