Here's a new article from iHobo, about the under-explored potential of games of "Peace" (notgames):
http://blog.ihobo.com/2012/09/war-and-peace-regimes-of-play.htmlAs opposed to "War", "Challenge", or "Puzzle", there is "Peace", and that is where the most innovation is happening now.
Art/games since 2005 (the year of both Façade and The Endless Forest) have been experimenting with what can be offered in this space, with Dear Esther and Proteus being recent additions to the artistic exploration of the kinds of thin play only possible under a Peaceful regime. It seems far more likely that innovative play experiences will come out of this side of the regimes of play than out of the well-worn track of War, Challenge and Puzzle
It's interesting to see the many ways that traditional game design thinkers conceptualize notgames.