24. The system of claim 14 , wherein generating the score comprises: identifying items of a first type ordered in common between the first and second plurality of items; identifying items of a second, different type ordered in common between the first and second plurality of items: and weighting each of the identified common items as a function of the respective type of the identified common item.
25. The system of claim 24 , wherein the weights associated with the first and second types of items ordered in common are determined based on a prioritization provided by the first user with respect to the first and second types of items.