1. A computer-implemented method for disseminating a plurality of message posts, comprising: in a server system having one or more processors and memory storing a plurality of message posts and one or more programs for execution by the one or more processors: selecting, from the plurality of message posts, one or more messages based at least in part on a focus specification associated with the respective user, the focus specification comprising one or more selection criteria; sending to a respective client system of the respective user at least a subset of the one or more selected messages; receiving a user selection of one or more anchor messages from the subset of messages; and sending to the respective user messages subsequent to the one or more anchor messages in respective threads associated with the one or more anchor messages.