1. A computer-implemented method for identifying social relationships for a first user operating in a first network context controlled by a first entity, comprising: generating an identity of the first user with reference to a first data source associated with the first network context and under control of the first entity, and at least one external data source outside of the first network context and not under control of the first entity; identifying a plurality of contacts having a relationship with the first user with reference to the first data source, the at least one external data source, and the identity of the first user, first ones of the contacts not being identifiable from the first data source; and determining a relevancy measure for each of the contacts which represents a relevance of the relationship between the first user and the contact, the relevancy measure for each contact being determined with reference to one or more of the first data source or the at least one external data source.