1. A method for identifying and messaging multiple targeted users of a communications system, the method comprising: executing instructions on one or more processing devices such that the one or more processing devices perform the following: before identifying a subset of multiple users to which a message is to be sent: accessing targeting rules that define parameters for identifying users to which the message is to be sent, the parameters specifying at least a target geographic location; accessing context information for the multiple users, the context information indicating at least geographic locations of each of the multiple users; applying the accessed targeting rules to the accessed context information to determine which ones of the multiple users are located within the geographic location; identifying a subset of the multiple users based on the application of the accessed targeting rules to the accessed context information, the identified subset of the multiple users including the users determined to be located within the geographic location, wherein the identified subset of the multiple users includes more than one of the multiple users but less than all of the multiple users; generating the message; and sending the message to client devices of the identified subset of the multiple users such that the message is displayed by the client devices.