Systems for forming and maintaining spontaneous networks of collaborators in shared content management systems. A shared content management system supports user interactions with content objects. A service of the content management system monitors occurrences of interactions between users and objects. The users are associated with collaboration groups. To generate recommendations of groups other than the collaboration group or groups in which a particular user is already a member, a method embodiment receives entity relationship scores from the service. An entity relationship score quantifies a relationship between two subject entities that are common to a particular entity interaction event. The method then assigns the subject entities to one or more spontaneously-generated clusters. As clusters are formed and populated, cluster affinity scores are continuously calculated. Periodically, a recommended cluster is selected based on a corresponding cluster affinity score. A recommended cluster is named based on the member entities of the recommended cluster.