2. The system of claim 1 , wherein the computer-executable instructions further cause the one or more hardware processor devices to: provide one or more instances of a collaborative user interface presentation for use by users in a group of users, including the particular user, each instance of the collaborative user interface presentation revealing messages entered by the users in the group.
6. The system of claim 2 , wherein the computer-executable instructions further cause the one or more hardware processor devices to: maintain a group profile for the group of users, the group profile describing media selections made by the group of users over a span of time, each entry in the group profile including: an identity of a prior media item that has been selected; and context information pertaining to a circumstance in which the prior media item has been selected.