1. A method comprising: identifying a plurality of connections of a user, each connection comprising another user of a social networking system with whom the user has established a relationship in the social networking system; for each of at least a plurality of pairs of the connections, determining a measure of affinity between the pair of connections based at least in part a number of friends in common between the pair of connections including: determining a measure of overlap of other users with whom the pair of connections have commonly established the relationship in the social networking system and who have been determined to be closely associated with the pair of connections, wherein the other users with whom the pair of connections have commonly established the relationship are determined to be closely associated with the pair of connections based on their historical interactions in the social networking system; iteratively clustering the connections into one or more clusters by performing the following, by a computing system: identifying two or more connections associated with the highest measure of affinity, collapsing the identified connections into a new cluster, recomputing new measures of affinity between the new cluster and each of the remaining connections and other clusters, and stopping the clustering when the remaining highest measure of affinity is below a threshold; and outputting a result of the clustering, the result comprising an identification of the clusters and the user's connections who have been assigned to the clusters.