I would never do this. People that steal from Goodwill make me sick. I have to admit that I do benefit from people stealing from Goodwill. Let me explain.
I have 2 Goodwills near my house, they're both about 2 miles away. They keep a lot of the real vintage video game stuff in glass cases. But then they put all their PS1, PS2, Xbox, Gamecube, and various other games over with the CDs and DVDs on racks. I've found that most of the time when you find a Final Fantasy game over there (especially FF 7) or a lot of other popular games like the Halo series or Metal Gear Solid series, that it's just an empty case over there. This is because douche bags have gone and shop lifted the discs out them. Now most of the time these cases still have the manuals and everything, so I'll round up the ones that look good and let the employees know that someone has shoplifted the discs out of them. Since they are now pretty much worthless to them they usually just let me take them for free. If I'm taking like 5 or more I'll usually pay them like 2 bucks for them, it's still worth it to me. Now I end up with a bunch of manuals and cases to sell, use to upgrade my collection, or use to put with games I've gotten really cheap as disc only. I make a nice little amount of money doing this to keep my collecting habit going.
I sometimes feel kind of bad about it because I wouldn't have this hookup if people weren't assholes shop lifting from a charity thrift store. But I figure it's ok since the employees tell me it's cool and I'm probably doing them a favor cleaning out the crap off there shelves. Plus like I said if I take more than a few I'll still offer to pay a couple bucks for it.
I will tell you this though, if I ever saw someone shop lifting from a charity, the shoplifter probably wouldn't be the only one going to jail that day...