1. A system for vending copies of a digital work, the system including: a computer system for receiving a plurality of bids from a plurality of bidders, wherein a maximum number of copies of the digital work subject to vending is not specified in advance of receiving the plurality of bids; a memory for storing the bids; bid sampling logic for selecting (i) a bid from a bidder, and (ii) a sample of one or more bids from the plurality of bids, wherein the sample does not include the bid from the bidder; a processor for deriving a threshold from the sample of bids, and for comparing the bid of the bidder with the threshold to determine whether to vend a copy of the digital work to the bidder as a function of the comparison, the threshold chosen to maximize a quantity obtained by multiplying (a) a number of bids in the sample that exceed the threshold by (b) a bid value of a highest bid in the sample that is less than or equal to the threshold; and a network interface unit for sending a copy of the digital work to the bidder.