Ask YC: Success innate or practice?

Malcolm Gladwell's (author or Blink and Tipping Point) has a new book, Outliers. He makes a variety of interesting and somewhat provocative claims about why successful people are successful. Perhaps the most provocative claim is that it requires 10,000 hours of practice to become and expert in anything. The implications of this include that Bill Gates and Bill Joy were so successful because of the opportunities they had to practice programming from Middle School (for Gates) and at UMich (for Joy). Do people buy this? How much of success is brilliance and how much is this amount of practice?