1. A system for providing flexible message-based communications over a centralized messaging infrastructure, comprising: a controller, comprising: an interface to a plurality of devices interconnected over a digital data network, each device being physically located at a location distinctly removed from each other device; a security module configured to provide security to digital voice messages exchanged with each device by applying encryption using a key unique to each of the devices; an access module configured to process a sign-in requested by a user via at least one of the devices; and a session module configured to form a plurality of voice message sessions for the user associated with the at least one device and, for each of the voice message sessions, to add the user associated with the at least one device to a discussion group; and a voice message server configured to centrally transact the voice message sessions, comprising: a message queue configured to receive the digital voice messages for the at least one device, to associate a user identifier and a discussion group identifier with each of the digital voice messages, and to transiently store the digital voice messages; and a queue manager configured to route the transiently stored digital voice messages to another of the devices, wherein logical participation in a plurality of the discussion groups is provided through exchange of the digital voice messages between the at least one device and each other of the devices in the discussion groups.