Thank you, but I want to point out I'm driven by selfish reasons just like anybody else: spending your life on something you hate/don't believe in is the recipe for alienation.

Also, I suspect a lot of companies are exploiting the fact that bright people in our field will be happy to work on stuff they don't believe in as long as you throw interesting problems at them. It's a tradeoff I can understand, but it still is a tradeoff. To answer your question, I'm 25.