2. The method of claim 1 , wherein said promotional offers relate to a plurality of products organized in taxonomic product groupings, and the method further comprises: providing a product grouping probability profile associating with each said product grouping a measure of the probability that a customer will purchase a product from said product grouping; and deriving said score for each said combination of customer and promotional offer from the measure of probability associated with each product grouping containing a product subject to the promotional offer.
2. The method of claim 1 , wherein said promotional offers relate to a plurality of products organized in taxonomic product groupings, and the method further comprises: providing a product grouping probability profile associating with each said product grouping a measure of the probability that a customer will purchase a product from said product grouping; and deriving said score for each said combination of customer and promotional offer from the measure of probability associated with each product grouping containing a product subject to the promotional offer. 7. The method of claim 2 , further comprising: providing access to a transaction history database for at least a substantial portion of said plurality of customers, wherein the database associates with each customer of said substantial portion an identification of transactions engaged in by the customer and an identification of products previously purchased by the customer in each of the transactions; providing a transaction summary data structure associating with each said customer the total number of transactions the customer has engaged in and the numbers of transactions including each said product grouping; averaging the product groupings per transaction from said transaction summary data structure for at least a portion of said customers; and deriving said measure of probability associated with each said product grouping from the averaged product groupings per transaction for the associated product grouping.