I'd like to say I hate the idea of taking games back. You bought it, you should have to keep it unless it doesn't work. It's a free rental basically, which for you is great, but for someone else who goes in there to pay for a new game it means they pay full price for a used game. I refuse to buy new games anymore because I wasn't getting new games anymore. Even on the first day it was out, the games were open and scuffed because they employees were taking them home to upload to the net.
Plus if they DO put it in the used game section, you only save 5 bucks. So you pay 45 because you know it's barely used, but whoever made the game sees ZERO royalties on the additional sales. It's all profit for the store.
I hate those stores now, they're ruining the industry. If they stopped selling used games in this fashion you'd see much less of a "we're hurt by pirates" attitude. Gamestop are the biggest pirates to the videogame industry.