It’s always great when I discover a succinct essay or lecture that summarizes the state of the union for a particular industry, art form or research topic. The other day I watched this half-hour talk by Carnegie Mellon professor Jesse Schell discussing trends in casual gaming. He starts a little slow but gathers steam:
Here’s a kind of response to Schell’s lecture, specifically discussing this idea of external rewards.
DarrenBarefoot.com 
I wish every lecturer sounded as much like Mitch Hedberg as this guy! Awesome stuff.