In one implementation, a computer-implemented method includes receiving at a server information indicating activity levels of users of a computer-implemented social network or acquaintance relationships of the users on the computer-implemented social network. The method further includes generating by the server influence scores for the users based on the received information. The method also includes recursively propagating by the server an ad through the computer-implemented social network between users having an acquaintance relationship by transmitting the ad from a propagating user to a recipient user when a difference between a first influence score of the propagating user and a second influence score of the recipient user is greater than a threshold.