Stupid move in the first place. There was no business advantage to dropping the Call of Duty name.
Everyone should know that it's Infinity Ward's sequel, but you have some people who didn't have a clue on what the game was...
EDIT: Notice (if this is the official box art) that the Call of Duty is smaller than the Modern Warfare 2 part. I think they are trying to get people to recognize the Modern Warfare part because they will probably drop Call of Duty in the next game. Trying to emphasize on that one part.