A method and system for creating and maintaining databases of user profiles and value ratings for information sources, and for generating lists of information sources having high estimated values. User controlled systems for accessing information sources through the internet or other networks are monitored by a server. The server updates the user profiles and computes value ratings associated with the user profiles for various information sources in accordance with monitored information. Estimated values for information sources to a particular user are obtained as a function of the value ratings associated with profiles of other users and the degree of similarity between the particular user's current profile and other user profiles. Previous profiles are not deleted when updated but are retained and treated substantially as other profiles in computing value estimates. Information sources can be other users.