I found instructive to compare two short videos from the STVP. The first one is dated 2002 and shows Larry Page, the co-founder of Google. The seconde one, with Aaron Levie, has just been published on january 19, 2011.

And here is a comparaison

Clearly passion, ambition but also self-confidence are ingredients of entrepreneurship.

Another very good post on the topic is Should You Really Be A Startup Entrepreneur? by Mark Suster, where the reality of entrepreneurship is superbly described.