1. A method comprising: accessing interaction data describing interactions between a plurality of actors of the online social network service and one or more content items posted on the online social network service; identifying, based on the interaction data, a specific content item posted by a particular actor of the plurality of actors and interactions by other actors of the plurality of actors with the specific content item; calculating, by a machine including a memory and at least one processor and based on the interaction data, a leadership score associated with the particular actor, the leadership score indicating a propensity of the particular actor to spread information among the plurality of actors of the online social network service; and classifying the particular actor as an information propagator among the plurality of actors of the online social network service, based on the calculated leadership score.