Every keynote since the invention of keynotes ends with the same advice: Do what you are passionate about. After reading Mark's blog, I am starting to question this advice. Were all the successful entrepreneur passionate about their ideas way before they created their companies or did passion come after that.
For instance, was Zuck wholeheartedly passionate about social networks when he was in high school that he decided to pursue that passion and build Facebook in college? Or did that passion come while and after building the website and seeing all the responses he was getting?