Actually, that was only a test-run they did in Hawaii, and you only had to trade in $50 worth of games.
Not trying to sound like I'm sucking up to the company I work for, but honestly it's not that bad of an idea. Someone who actually has $50 worth of games to trade is probably a true gamer, and therefore is not as likely to just be pre-ordering the system to sell on eBay.
At any rate, it was only a test that they were doing, and we haven't heard anything about it here in the rest of the company. So I'm not sure whether they are going to do that for all of the other stores.