1. A method of administering instant messaging (IM), comprising: receiving input from a plurality of subscribers in a conversation associated with a persistent-IM-group; wherein the input is associated with the persistent-IM-group using a persistent-IM-group identifier that uniquely identifies the persistent-IM-group; storing, at an instant messaging server, subscriber-to-identifier information that associates the plurality of subscribers with the persistent-IM-group identifier; accessing the subscriber-to-identifier information to determine to whom to send messages that are part of the conversation associated with the persistent-IM-group; sending over a network, to each subscriber of the conversation, messages to allow the subscriber to view contents of the conversation; after all sessions associated with the persistent-IM-group identifier have been terminated: persistently storing, at a centralized server, the contents of the conversation in association with the persistent-IM-group identifier; establishing a new session associated with the persistent-IM-group identifier with at least one of the plurality of subscribers; during the new session, allowing the at least one subscriber to see the persistently stored contents of the conversation associated with the persistent-IM-group identifier; within the new session, receiving new input that represents new content for the conversation from the at least one subscriber of the plurality of subscribers; by accessing the subscriber-to-identifier information, sending, over the network to each subscriber that is currently in a session associated with the persistent-IM-group at the time the new input is entered, messages to allow the subscriber to view the new content of the conversation; by accessing the subscriber-to-identifier information, sending, over the network to each subscriber that establishes a session associated with the persistent-IM-group after the new input is entered, messages to allow the subscriber to view the new content of the conversation; persistently storing at the centralized server the new content in association with the persistent-IM-group identifier as new content of the conversation ; receiving an explicit request to end the persistent-IM-group; and in response to receiving the request, ceasing to allow subscribers to establish sessions associated with the persistent-IM-group identifier; wherein the method is performed by one or more processors.