1. A method comprising: by one or more computing devices, receiving, from each of a plurality of users, a posting request to a social networking system and a location associated with the posting request; by the one or more computing devices, assessing social and spatio-temporal proximity to identify a common location and a common time instance between or among a subset of the users based at least in part on the location associated with each of their posting requests; by the one or more computing devices, based on the assessment, creating a shared space for the posting requests of the subset of the users that are within a threshold spatio-temporal proximity; by the one or more computing devices, based on the assessment, creating a concept node in a social graph maintained by the social networking system, the social graph comprising a plurality of nodes and a plurality of edges connecting the nodes, and wherein: the concept node corresponds to the shared space, and each of a plurality of user nodes corresponds to a user of the plurality of users; by the one or more computing devices, based on the assessment, creating, for each user of the plurality of users, an edge connection between the user node corresponding to the respective user and the concept node corresponding to the shared space; by the one or more computing devices, composing one or more content items from one or more of the posting requests of the subset of the users; and by the one or more computing devices, during the common time instance, adding the content items to a dynamic list of content items associated with the shared space.