Assisting participation in a social network

Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for assisting participation in a social network. In one aspect, a method is performed by a system of one or more data processing devices. The method includes receiving, at the system, a historical record of message exchange between an individual and members in a member network, the system determining, for each of the members, whether the individual is likely to want to be related to the respective member, each determination considering the number and transactional characteristics of the message exchange between the individual and the respective member in the historical record, and the system outputting the determinations that the individual is likely to want to be related to at least two of the respective members.