1. A method implemented by a computer system, the method comprising: determining, by the computer system, a set of labels to be associated with users of a social network, the labels including one or more designators for specifying areas of interest and areas of disinterest for a user; associating, by the computer system, one or more of the set of labels to nodes in a graph that represent the social network, wherein the users are represented by user nodes in the graph; determining that a user is similar or dissimilar to another user in the social network, including determining a measure of similarity between the user and the other user, wherein the measure of similarity includes a similarity score determined from user interests and disinterests associated with a respective user, wherein the similarity score is based at least in part on similarity or dissimilarity of the user and the other user; determining, by the computer system for each respective node, weights for the labels, each weight reflecting a magnitude of a contribution of an associated label to a characterization of the respective node; and propagating labels for a respective node to other nodes that are related to the respective node by a relationship including propagating labels in accordance with the determined measure of similarity including, when propagating labels between two nodes that have been determined to be dissimilar based on the determined similarity score, propagating areas of interest of one node of the two nodes as being of disinterest to another node of the two nodes and areas of disinterest as being of interest to the another node.