In general, the subject matter described in this specification can be embodied in methods, systems and program products. A server system receives from a plurality of computing devices indications that a user of each of the computing devices requested to receive posts that a first user authors. The server system receives from a first computing device a post that was authored by the first user. The post is transmitted from the server system to the plurality of computing devices. A score for the post is determined to satisfy a criteria for transmission to a second user who has not requested to receive posts authored by the first user. The determination uses a distance of the second user to the first user in a social network graph. In response, the post is transmitted from the server system to a second computing device that is associated with the second user.