Selecting prospective bidders to whom to promote an online auction based upon bidding history

A facility for identifying users to whom to promote a selected auction is described. The facility maintains a representation of bidding histories of a plurality of users. At a point at which certain users have already bid in the selected auction, the facility identifies users that have not already bid in the selected auction that have bidding histories that are similar to those of users that have already bid in the selected auction. The facility then promotes the selected auction to the identified users.