1. A method comprising: assigning a plurality of interactive virtual advertisement spots to a program; generating a retrieval plan; and providing the retrieval plan to a terminal, wherein the retrieval plan instructs the terminal to display in one of the virtual advertisement spots an interactive virtual object selected from a ranked list of a plurality of interactive virtual objects, wherein said ranked list is determined at least by a measure of effectiveness for each one of said plurality of interactive virtual objects in each one of said plurality of interactive virtual advertisement spots, wherein each one of the plurality of interactive virtual advertisement spots is in a different spatial location in said program.