21. The computer system of claim 16 , wherein analyzing the user activity data comprises comparing item popularity levels associated with the subset of users to corresponding item popularity levels associated with the plurality of users.
16. A computer system comprising one or more computers, said computer system programmed, via executable code stored in computer storage, to perform a method that comprises: storing, in an electronic data repository, user activity data associated with each of a plurality of users of an interactive system that provides access to an electronic catalog, said user activity data reflecting user-generated events associated with particular items represented in the electronic catalog; identifying, among the plurality of users, a subset of users whose email addresses are associated with a particular organization; analyzing the user activity data associated with the plurality of users, including the subset of users, to identify, among the items represented in the electronic catalog, a set of items that have experienced significantly higher levels of user activity among the subset of users than among the plurality of users; and storing, in computer storage, association data that associates the organization with the identified set of items.