Particular embodiments evaluate a plurality of messages. Each message may be associated with an author. Information may be logged for each message, such as information associated with the author, information associated with one or more designated recipients of the message, and time information. Correlation values may be determined for one or more sets of designated recipients based on at least a portion of the logged information. Particular embodiments may determine an association amongst a plurality of users over time. The determination may be based on the correlation values. At least one of the plurality of users may comprise at least one of the designated recipients.