1. A user-interface method of presenting and selecting a collection of content items to infer preferences of a given user from a plurality of users of an input interface, the preferences of the plurality of users of the input interface being learned based on content items selected by the plurality of users, the method comprising: providing access to a set of content items, each content item having at least one associated descriptive term to describe the content item; receiving incremental inputs through a shared input interface; in response to said incremental input, presenting a corresponding subset of content items; receiving from the shared input interface selection actions of content items; analyzing the descriptive terms associated with the selected content items to learn a composite set of preferred descriptive terms of the plurality of users of the shared input interface, wherein the shared input interface used by the plurality of users is an input interface used by each user of the plurality of users so that the composite set of preferred descriptive terms collectively describes the descriptive terms associated with content items selected by each of the users of the plurality; for at least one of the individual users of the plurality of users of the shared input interface, creating an individual preference signature that characterizes the preferred descriptive terms that correspond with said at least one individual user based on the composite set of preferred descriptive terms and based on prespecified statistical models of preferences of a population according to demographic information; and reporting information about at least one of (i) the preferred descriptive terms characterized by the individual preference signature and (ii) the at least one individual user corresponding to said individual preference signature.