Well this sounds like a pretty vague question but please bear with me.
I know of how Gaiaonline gave gold to people who participated in forum posts.
I'm curious if in theory these could be applied to social aspects of games like Second life or Sims Online.
The question what would be specific quantifiable actions/interactions could be measured tracked for rewards and achievements that would help build a community?
(this'll probably end up as community wiki though)