Yahoo identifies five different competitiveness levels for social communities (Caring, Collaborative, Cordial, Competitive, Combative) and recommends different ways of handling reputation in your system based on the behavior of its users. I found it very insightful to break down behavior in this way as point systems work better in competition, for example, while named labels help in caring and collaborative situations. Looking forward to more of this sort of stuff from Yahoo! Original blog post at the yuiblog.