14. The computer program product of claim 13 wherein the first collection of entities is named, and wherein the instructions further include instructions that cause the one or more processors to provide to the content sponsor an interface for enabling a selection of the first collection of entities from a plurality of available collection of entities, and receive from content sponsor an explicit designation of the first collection of entities by name to be used as the selection criteria for delivery of the first content item.
15. The computer program product of claim 14 wherein the explicit designation includes a designation of the first collection of entities and an amount of a bid to be used when evaluating the first content item with other eligible content items in an auction or reservation selection system.