1. A computer implemented method comprising: providing access to a plurality of applications provided by third-party developers on a social networking system; receiving information about a plurality of interactions of a plurality of users of the social networking system, the interactions relating to one or more of the applications, each interaction associated with one of a plurality of action types, each action type associated with a measure of affinity of a user for an application; aggregating the interactions of the plurality of users for a subject application of the plurality of applications based on the action types; determining, by the social networking system, a user affinity score for the subject application indicating affinity of the users of the social networking system for the application, the user affinity score based at least in part on the aggregated interactions, weighted based on the action types of the interactions; and receiving, by the social networking system, request to send one or more messages associated with the subject application; and determining whether to send the one or more messages based on the user affinity score for the subject application.