Why didn't Zuckerberg sell?

In the article How Mark Zuckerberg Turned Facebook Into the Web's Hottest Platform it talked about Zuckerberg and the money he turned down for Facebook, I might be able to understand a bit why he didn't sell after all. He put a tremendous amount of himself into this project. Years of his life. It is a huge accomplishment just as it is now. But he has bigger plans, things he wants to see happen, ways in which he wants to see the site evolve. If he sold out and turn his creation over to someone else, he would no longer have any hand in its growth and evolution. Even with $1 billion dollars, how could you walk away from something you put so much of yourself into creating?