1. A method for displaying content comprising: receiving, by one or more processors, content items that are publishable to an activity stream in a social networking application for a user in a social network; evaluating, by the one or more processors, the received content items using social criteria, including determining a social quality score for each content item, based at least in part on a measure of a likelihood, upon publishing each content item, of a specific social interaction with the content item and value to the social network of the specific social interaction, including measuring and determining probabilities associated with engagements that users have had with previously-presented content items and that users may have with content items that may be presented in the future; filtering, by the one or more processors, the received content items to remove content items having social quality scores below a predetermined threshold; ranking, by the one or more processors, remaining content items according to their associated social quality scores; and publishing, by the one or more processors, the remaining content items in the activity stream for the user in an order based at least in part on the ranking.