According to Wil Shipley of Delicious :
I believe the best software is written by small groups of people who have both passion and vision. Passion is easy to define; you care so deeply about something that it wounds you if it’s done poorly. Vision can mean different things, but I mean the ability to not just come up with new ideas, but to actually be able to see how they would integrate with people’s lives. Vision without passion gives you a guy who sitting on couch saying, “Flying cars! Wave of the future! Mark my word, the guy who invents that’s going to be rich … pass the chips.” Passion without vision gives you America’s current political situation, where we allow huge companies to destroy the world but pass laws to make sure nobody marries a turtle.