1. A computer-implemented method comprising: selecting one or more users that are connected to a particular user by way of a social networking service or by a relationship described by a graph stored in a database, wherein each user interacts with one or more services; accessing, for each of the selected users, an interest score of the selected user that reflects the selected user's predicted interest in the particular topic, or interest data that that is used to determine the interest score of the selected user; accessing a model that is used for generating the interest score of the particular user that reflects the particular user's predicted interest in the particular topic, wherein the interest score of the particular user is generated based at least on the interest scores or interest data of the selected users for the particular topic; and applying the interest scores or interest data of the selected users for the particular topic to the model to generate the interest score of the particular user for the particular topic.