1. A computer implemented method of retrieving information, comprising: receiving a query and user information indicative of a user that initiated the query; receiving search results based on the query; utilizing a computer processor that is a component of the computer to apply to the search results a user class model that models a first set of user classes by grouping a plurality of users into multiple classes based on a first portion of an IP address of the plurality of users, said first portion being less than the complete IP address, and wherein applying the user class model to the search results further comprises applying the user class model so as to compare the user information to the first set of user classes so as to determine which of the search results are most likely desired by the user; applying to the search results a backoff model that models a second set of user classes by grouping the plurality of users into multiple classes based on a second, smaller portion of the IP address of the plurality of users, said second portion being less than the complete IP address, and wherein applying the backoff model to the search results further comprises applying the backoff model so as to compare the user information to the second set of user classes so as to determine which of the search results are most likely desired by the user; ranking the search results based on said applications of the user class model and the backoff model, wherein ranking the search results comprises ranking the search results not based on a complete indication of the identity of the user as reflected in the complete IP address but instead ranking the search results based on an incomplete indication of the identity of the user as reflected in the user class model and the backoff model; and returning the ranked search results to the user.