1. A method comprising: receiving, by a social networking computer system, an advertisement request from an advertiser to sponsor stories for display to a plurality of viewing users in a social networking system; identifying an indication in the advertisement request of: a type of action by other users with whom the viewing users have connections, the type of action selectable by an advertiser from a plurality of types of actions provided to the advertiser by the social networking computer system, and an instruction to provide messages to the viewing users that the other users connected to the viewing users in the social networking system have performed actions of the indicated type of action; receiving, by the social networking computer system, a bid amount for the advertiser to sponsor stories that match the advertisement request to accelerate the sponsored stories such that the sponsored stories are published in a news feed though at least some of the stories would not have otherwise been selected for publication without sponsorship; logging, by the social networking computer system, information related to actions taken by the other users of the social networking system who have connections to the viewing users; for each of the viewing users: generating, by the social networking computer system based on the logged information, a set of stories that is personalized for the viewing user such that each viewing user has a different set of stories, each story comprising information about at least one of the actions taken by a user of the social networking system who has a connection to the viewing user; computing, by the social networking computer system, an affinity score between the viewing user and at least some of the generated stories, the affinity score for each of the stories based on the viewing user's affinity for the user who took the action described in the story; using the logged information and the indicated type of action in the received advertisement request to match the advertisement request to one or more of the stories to identify stories for sponsorship based on the story comprising: an action that corresponds to the type of action indicated in the advertisement request; selecting, by the social networking computer system, stories for display in a user interface for the viewing user, the selected stories comprising: (1) a set of stories identified based on the affinity scores indicating affinity for the story above a threshold level, and (2) one or more of the stories identified for sponsorship, the stories identified for sponsorship having been accelerated relative to others of the stories generated based on the the bid amount; generating a news feed customized for the viewing user that includes the one or more of the stories identified for sponsorship interspersed with the selected set of stories; and providing for display in user interfaces for each of the viewing users the generated news feed that is customized for the viewing user such that different stories are included in the news feed for different viewing users.
1. A method comprising: receiving, by a social networking computer system, an advertisement request from an advertiser to sponsor stories for display to a plurality of viewing users in a social networking system; identifying an indication in the advertisement request of: a type of action by other users with whom the viewing users have connections, the type of action selectable by an advertiser from a plurality of types of actions provided to the advertiser by the social networking computer system, and an instruction to provide messages to the viewing users that the other users connected to the viewing users in the social networking system have performed actions of the indicated type of action; receiving, by the social networking computer system, a bid amount for the advertiser to sponsor stories that match the advertisement request to accelerate the sponsored stories such that the sponsored stories are published in a news feed though at least some of the stories would not have otherwise been selected for publication without sponsorship; logging, by the social networking computer system, information related to actions taken by the other users of the social networking system who have connections to the viewing users; for each of the viewing users: generating, by the social networking computer system based on the logged information, a set of stories that is personalized for the viewing user such that each viewing user has a different set of stories, each story comprising information about at least one of the actions taken by a user of the social networking system who has a connection to the viewing user; computing, by the social networking computer system, an affinity score between the viewing user and at least some of the generated stories, the affinity score for each of the stories based on the viewing user's affinity for the user who took the action described in the story; using the logged information and the indicated type of action in the received advertisement request to match the advertisement request to one or more of the stories to identify stories for sponsorship based on the story comprising: an action that corresponds to the type of action indicated in the advertisement request; selecting, by the social networking computer system, stories for display in a user interface for the viewing user, the selected stories comprising: (1) a set of stories identified based on the affinity scores indicating affinity for the story above a threshold level, and (2) one or more of the stories identified for sponsorship, the stories identified for sponsorship having been accelerated relative to others of the stories generated based on the the bid amount; generating a news feed customized for the viewing user that includes the one or more of the stories identified for sponsorship interspersed with the selected set of stories; and providing for display in user interfaces for each of the viewing users the generated news feed that is customized for the viewing user such that different stories are included in the news feed for different viewing users. 9. The method of claim 1 , wherein the one or more stories identified for sponsorship are provided to the viewing user as unsponsored newsfeed stories in other contexts.