A multi-social network discovery system and method enables users to select multiple social networks comprising activity streams and to receive recommendations sourced from the selected multiple social networks. The multi-social network discovery system and method generates affinity values based on inferred affinity levels between topics, which may be associated with tags, and objects that are associated with the activity streams. The inferred affinity values may be derived from usage behaviors such as tagging and/or based on an automatic analysis of the content of the objects. The affinity values inform the selection of the objects to be recommended to a user, and the selection may be further informed by inferred affinity levels between the user and the topics. The recommendations may be tuned by the user through application of a recommendation tuning control.