Taxonomy of social mechanics in multiplayer games

Yesterday's Game Developer Conference in San Francisco saw a smashing presentation from game-design legend Raph Koster, entitled, "Social Mechanics: The Engines Behind Everything Multiplayer." Alice from the Wonderland Blog took copious notes, and Raph has uploaded his slides.
#5: Tournaments: bracketing users. Social games tend to use bracketing for simple pvp matchmaking: it's under utilised.

#6: Opposition. A rival good is something that can't be used by someone else at the same time. You have my stuff, I can't use it. Non-rival is stuff that clones itself: information, etc.

#7: Dot-eating. I ate it, you didn't. Zero sum resource consumption.

#8: Tug of War. A winner and a loser.

#9: Handicapping.

#10: Secrets. Fog of War. Hands of cards.

#11: Last man standing. Deathmatch.

Social Mechanics: The Engines Behind Everything Multiplayer (PDF)

Raph's 40 social mechanics for social games (Wonderlandblog)