Steve was a natural performer who elevated business presentations to something close to high art. But what made him fidgety this day was the prospect of addressing the Stanford University graduating class of 2005. University president John Hennessy had broached the idea several months earlier, and after taking just a little time to think it over, Steve had said yes. He was offered speaking engagements constantly, and he always said no. In fact, he was asked to do so many commencement addresses that it became a running joke with Laurene and other friends who had college or graduate degrees: Steve said he’d accept one just to make an end run around them and get his PhD in a day, versus the years and years it had taken them. But in the end, saying no was simply a question of return on investment—conferences and public speaking seemed to offer a meager payoff compared to other things, like a dazzling MacWorld presentation, working on a great product, or being around his family. “If you loo...