1. A machine-implemented method comprising: receiving, by one or more computing devices via an electronic network, an indication that a first user has interacted with a second user in an online social network; calculating, by the one or more computing devices in response to receiving the indication, a social affinity score between the first user and the second user based on first user information, second user information, or relationship information between the first user and the second user; selecting, by the one or more computing devices for a computer-implemented notification related to the indication that the first user interacted with the second user, one of a plurality of predetermined delivery actions based on the social affinity score, the plurality of predetermined delivery actions comprising immediately delivering the notification for display to the second user and delivering the notification for display to the second user after a predetermined time period has elapsed together with one or more other notifications delivered after the predetermined time period; and delivering, by the one or more computing devices via the electronic network, the notification according to the selected one of the plurality of predetermined delivery actions for the notification.