Methods and systems for identifying communities based on information propagation data are described. One of the methods includes receiving a social graph, which includes nodes and relationships between the nodes. The method further includes receiving a number of the communities to find within the social graph, receiving data regarding propagation of information between the nodes, and calculating a probability of formation of a link between a first one of the nodes and a second one of the nodes based on the data. The link provides a direction of flow of media between the first and second nodes. The method includes calculating a probability that media will be accessed by the second node based on the data. One of the communities includes the first node, the second node, and the link.