In case you don't recall Phillip's tool design post, libertarian paternalism states that the best system leaves people free to make their own choices yet nudges them towards the best choices. As demonstrated by the The Fun Theory video below, making an activity more fun, is a great way to coax more people to do it.
When the fun of the piano stairs overpowers the convenience of the escalator, people choose to take the stairs thus getting a little bit of exercise.
Here's another example. Entering data into a data base is an awful chore. However, the Google Image Labeler has done a decent job of of turning this chore into a game. I've probably helped optimize the tags for 50 pictures now and I felt like I was playing rather than working.
Even if activities have high payoffs to us or our society, when they feel like chores, it's hard for us to will ourselves to do them. Fortunately, with a little game design in the right places, it is often possible to make labor seem more like leisure. Overgrowth probably won't have any grandiose incentives that attempt to leverage fun to create world peace. However, our hope is that by including the easy-to-use editor suite with the game, we will nudge people to embrace their creativity and have a try at modding.
What do you guys think about libertarian paternalism and using fun as a method to encourage beneficial behavior? Can you think of other examples I didn't mention?