FORTUNE -- Just a couple of years ago, Mark Zuckerberg made few public appearances. When he did appear before a crowd, he often drew snarky criticism for his difficulty expressing himself. As an ubergeek, he's still an unlikely public speaker. And yet his keynote at Thursday's f8 conference shows how far he's come and -- more to the point -- how much more willing people are to accept and even idolize him. It's amazing what a little time and a few billion dollars can do.