The real Mark Zuckerberg has taken measured issue with the way “The Social Network” portrays him. He has disputed, especially, the filmmakers’ suggestion that he built the site as a means to worldly ends. “They frame it as if the whole reason I invented Facebook was that I wanted to get girls or to get into some kind of social institution,” he told an audience at Stanford University in October. “They just can’t wrap their head around the idea that someone might build something because they like building things.”I note the alternative motives here: sex or curiosity, not money. The book, "The Facebook Effect", which I just finished, is consistent with the movie in this respect. Zuckerberg is depicted almost as an artist with a pure vision of what Facebook could be, a vision which excludes lots of ads and commercialization and includes declining multiple opportunities to cash in for the big bucks.
So what's the role of money as an incentive? I'd suggest it plays a role in some choices, like an initial choice of occupation. I'm sure some people choose to work on Wall Street instead of Teach for America because of money. And many people who go into medicine may choose a specialty partially because of money. But I don't think money is that important in the big scheme of things. So why worry about the impact of taxes on incentives for work? The best answer is because taxes can be changed but you can't change sex or curiosity.