Brother Rubbish points me to a post at Counago and Spaves - worth a look. There's good stuff in the links on co-operation and free-riders, with references to the work of Mancur Olsen, and an interesting question: Is a free-rider a sociopath?
Sociopaths are "....incapable of cooperation with others beyond short-term exploitation.."
Ring any bells?
Brother Rubbish also posted this a few days ago on a tangential theme.