1. A computer implemented method for filtering an event notification stream based on relevance to specific targets in a distributed file sharing and collaboration environment in which multiple users collaboratively view, modify and comment on a shared set of files, the method comprising the steps of: maintaining, by a computer, dynamic and static profile information concerning each one of the multiple users, wherein user profile information concerning a user describes the user and quantifies an interest level of the user in specific files, specific types of files and specific file content of the shared set, and quantifies a similarity level of the user to other specific users and to specific types of users; maintaining, by the computer, file profile information concerning each file of the shared set, wherein file profile information concerning a file describes the file and quantifies a similarity level of the file to other specific files, specific types of files and specific file content of the shared set; filtering the event notification stream of the file sharing and collaboration environment, by the computer, wherein the event notification stream comprises a plurality of notifications, each notification describing an event undertaken by a user and directed towards a file of the shared set; for each specific event notification in the filtered event notification stream, quantifying a relevance value, by the computer, for each specific one of the multiple users, based on user profile information concerning the specific user, file profile information concerning the file to which the event is directed, and user profile information concerning the user who undertook the event; and transmitting, by the computer, a notification describing the specific event only to those specific users for whom the relevance value exceeds a predetermined threshold value.