If you've ever been interested in what keeps you coming back to your console/PC/mobile/handheld for more more more, Lost Garden has a pretty comprehensive list of the game mechanics he's implemented in the products he's created for Epic and other studios. Among them are Feedback Loops, Systems Linking Systems, Our Infovore Habits, Avoiding Burnout, Drop-Kicking Milking, Introducing Red Herrings and The Human Factors That Make (or Break) Games. If you are so inclined, you may recognise many of them from Raph Koster's Theory of Fun - a must for any designers out there.
Well worth a read, for any aspiring developers (and perhaps veterans too?).
It's pretty easy to apply Web 2.0 applications to these categories. They're becoming much more astute to how we like to play.
