According to public goods theory, there should be a deficiency of knowledge shared in electronic discussion groups (EDG) because self-interested individuals would be motivated to receive othersí knowledge but not to share their own. A number of motivators (such as generalized reciprocity, altruism, and normative obligations) have been proposed to explain why people actually do share their knowledge in such settings, and empirical research has confirmed that people do express these motivations for sharing their knowledge. However, the simple picture of individuals sharing knowledge that is known to be true limits our ability to understand what actually is going on in EDG. This paper develops a typology of interactions that may arise in electronic discussion groups and argues that several of these types of interactions confer benefits onto participants that may well motivate them to contribute their knowledge, even in settings where traditional motivators may be weak or absent. In particular, the process whereby anomalies are reconciled and the provision of knowledge to conduct remote-controlled experiments both stand to generate returns to those who contribute that are not available to those who ìlurk.î