GameStops jumping into the used iPods business would be news to me, but if it's already been going on, it sounds like it could be isolated to a few test-market stores. A purported GameStop computer screen showing database entries regarding tradable iPods showed up in a report on Kotaku, and though my local GameStop doesn't offer such a service, someone in the comment thread posted a photo of a store's window sticker that would seem to corroborate such a system.
Retail market tests by chains like GameStop are always tough to gauge when new programs start testing the waters, and this one may be in the works, on its way out the back door, or somewhere in limbo awaiting judgment from GameStop corporate, but now that the company has their own iPhone game, I do wonder if they'll offer to install it on your secondhand iPod touch for an extra fee if you buy one.
Multiple generations of iPod touches, iPod Photos and iPod Shuffles appeared in the screencapped listings, so the program looks like it will be be fairly inclusive. Apple's products have become much bigger players in the games industry since the App Store launched, and a place on the used hardware shelves at GameStop would certainly be a sign that the big-time name in trade-ins was looking to get some cashflow out of a part of the gaming world that it hasn't previously been siphoning.
Has your local GameStop been offering trade-in deals for iPods? Would you pick up a used iPod there if given a chance? Share your reactions with us in the comment section below.