In many situations of computer-supported collaborative learning, it is a challenge to increase the willingness of those involved to share their knowledge with other group members. To study a prototype of such a situation of computer-supported information exchange, we arranged a shared database setting as a basis of an empirical research program. This knowledge-exchange situation represented a social dilemma: while contributing information to a shared database led to costs and provided no immediate benefit to the individual, the entire group suffered when all members decided to withhold information. A series of experiments identified a multitude of influencing factors in this situation: group size, awareness of the importance of information, costs of entering information, use-related bonus systems, feedback and recommendations, and group awareness. This paper describes the impact of these factors on people’s willingness to share their knowledge with their cooperators, and concludes with a discussion of some practical consequences.