Any one here do this? By stores, I'm pretty much referring to GS.
I started doing this last year of out curiosity. Indeed it's tiring, and gross, but worth it I think. I've found so much stuff this way. Everything from pre-order bonuses, store displays, to complete games, and ones I wanted to add to my collection. A lot of the stuff is really profitable. I've made nearly a grand out of their dumpster.
For myself, most of what I hope to find is just DS cases. Since I'm such a big DS fan / collector, I like to find the cases to games still on my wishlist in hopes that I'll be able to obtain them cheaper, either through GS, or due to being less expensive cart only online. I also feel a personal duty to stop good DS cases (for good titles) from going to the landfill. But I also like finding all the different, neat and often times collectible stuff that gets thrown out.
Last night's run yielded a lot of good cases, and a disc only copy of Tactics Ogre. Not my cup of tea, but what a waste to be thrown out!
The downside is it eventually becomes a hoarding habit. I've accumulated so much stuff I can't possibly find a home for all of it. A lot of it I just wanna unload now, but I don't just want to throw it back out.