1. A computer-implemented method comprising: presenting one or more story units having a particular type to a plurality of users of a social networking system in an initial configuration, wherein a story unit includes one or more stories describing actions performed by a user of the social networking system and having a common characteristic; presenting one or more story units having the particular type to an additional plurality of users of the social networking system in an alternative configuration, the alternative configuration being different from the initial configuration; capturing one or more interactions by the plurality of users with the one or more story units presented in the initial configuration; capturing one or more interactions by the additional plurality of users with the one or more story units presented in the alternative configuration; and selecting a default configuration for story units having the particular type from the initial configuration and the alternative configuration based at least in part on the captured one or more interactions by the plurality of users with the one or more story units presented in the initial configuration and the captured one or more interactions by the additional plurality of users with the one or more story units presented in the alternative configuration.