2. The system of claim 1 wherein: the step of sending the first information to the first user causes display of the first information in a particular application display of the first user; and the method further comprises: receiving from the first user a third expression of interest in being notified about interactions of a fourth user that is different from the third user; and in response, at least in part, to a given interaction of the fourth user with the system, sending second information to the first user, based, at least in part, on the third expression of interest to cause display of the second information concurrently with the first information in the particular application display.
2. The system of claim 1 wherein: the step of sending the first information to the first user causes display of the first information in a particular application display of the first user; and the method further comprises: receiving from the first user a third expression of interest in being notified about interactions of a fourth user that is different from the third user; and in response, at least in part, to a given interaction of the fourth user with the system, sending second information to the first user, based, at least in part, on the third expression of interest to cause display of the second information concurrently with the first information in the particular application display. 8. The system of claim 2 wherein: the particular interaction corresponds to the third user loading at least a portion of a file to the system; the given interaction corresponds to the fourth user joining a group of users; and the second information includes a description of the given interaction.