Private provision of a public good: cooperation and altruism of internet forum users

We run an experiment with users of internet message boards. We find that forum users cooperate more with partners of their own forum than with partners from a different forum but they are equally altruistic when they made a gift to a partner of their forum or from another one. We also find that individuals are more active in the forums, the more altruistic they are; however, we find no relation between activity in the forum and cooperation. These results suggest that the public good provided in internet forums is mainly provided by a group of unconditional altruistic group of users, and that the feeling of community supports the cooperation in that provision.