All the Xbox fans are quick to jump on this with "Sony is getting desperate" (in the vein that Sony fans talked about MS for November's strategy for XBone)......but did any of you stop to realize that this isn't official from Sony? It's a retailer specific deal. Amazon is running the promotion, not Sony.
This isn't Sony saying "hey, trade in a PS3 or 360 and we'll give you $100 toward a PS4". This isn't Sony saying "hey, buy a PS4 this month, anywhere, and you'll get any free game you want". This isn't Sony "temporarily" dropping the price to get people to buy it now thinking the price will go back up (but probably won't).
This is Amazon doing whatever they want with the product they purchased from the manufacturer. I wish it was official. Then I could do it at Best Buy (because I have a card there :D). Apples to oranges. But good try, though, boys