Anybody who has ever ventured into the world of Usenet knows what can happen when there is absolutely no moderation. Arguments can quickly become hateful cesspools of libelous insults and cyber attacks that may even extend into the user's real life world of home and work. On the other hand, heavy moderation of posts kills spontaniety and user involvement. In other words, it's not fun anymore and users quit the group.
Pattern Language is a sort of meta-overview of how people react to structures of varying types. It was invented by a residential architect named Christopher Alexander, but interestingly enough, it works well with software design too. Alexander describes 3 parts to this tool: Context, System of Forces, Solution. A successful solution moderates the challenges of the System of Forces against the Context of the pattern (i.e., the way Ebay incorporates self-policing through it's buyer evaluation ratings for each seller).
As I read O'Reilly's notes on the talk Shirky gave, I was struck by the similarity of Pattern Language to a Go proverb - Play on the Point of Symmetry, which says: "When right and left have the same shape, there is play in the center."
