Possible Duplicate:
Automatically track referenced questions
Could a list of dupes linked to the current questions be added to the side like the related questions list?
It would be similar to the "what points here" in Wikipedia, and would allow for evaluation when deleting a question that has been marked as a dupe, but could conceivably have more uses.
It shouldn't stress too much the server if it is done denormalized and during the closing as duplicate.