It seems to be that Capcom making the new Mercenaries game unable to reset the game data has led to the game becoming untradeable. UK game retailer HMV have said that they will not be taking the Mercenaries game in as preowned.
This is due to the arcade style shooter creating highscores that cannot be overwritten. Capcom stated this would not affect the price of the game upon trade in and in a way they were right; it has no value it’s untradable.
It will be interesting to see if other game retailers take a similar stance on the most recent Resident Evil game.