That's what the shops around here have started doing; I went to pick up Tatsunoko vs. Capcom the other day, and they actually swapped the display case for a sealed one. 'Twas a pleasant surprise.
A question for anyone who's worked at GS: lately I've noticed the employees pushing used game sales harder, especially on recent games where the price difference is ~$5. Is that another thing management is trying to push, or do they just think they're being helpful?