1. A computer-implemented method comprising: receiving at a first server system information related to users of a social network site hosted on a second server system; determining by the first server system a social network graph for at least a portion of the social network from the received information, the graph comprising a plurality of nodes connected by links, each node corresponding to a user that is registered with the social network and that has a profile page on the social network; identifying first nodes from the plurality of nodes as including content associated with a particular subject of interest; seeding the identified first nodes with first scores that indicate profile pages for the identified first nodes are positively identified as including content associated with the particular subject of interest; determining second scores for second nodes of the plurality of nodes based on propagation of the first scores from the first nodes to the second nodes using the links of the social network graph, where: each of the determined second scores corresponding to a second node indicates a likelihood that a profile page for the second node contains content associated with the particular subject of interest, a particular second score for a particular second node is determined based on a combination of scores for neighboring nodes that are connected to the particular second node by one or more of the links, and a particular profile page that is associated with the particular second node is determined to have at least a threshold likelihood of containing content that is associated with the particular subject of interest when at least a portion of the scores for the neighboring nodes exceed a threshold score; and providing by the first server system the determined second scores for the second nodes.