1. A computer-implemented method comprising: receiving, at a computer system, user information associated with users of a social network and associated with media accessed by the users; generating, by the computer system, a graph having nodes of a plurality of categories that are linked together by edges from the received user information, wherein the plurality of categories includes at least a first category of user nodes that represent the users of the social network and a second category of media nodes that represent the media accessed by the users; selecting, by the computer system, a type of label to propagate in the graph; iteratively propagating, by the computer system, values for labels of the selected label type through nodes of the plurality of categories in the graph using the edges that link the nodes together; and outputting by the computer system, the iteratively propagated values for labels of the selected label type for the nodes of the plurality of categories in the graph.