Well, this thread is old and dead, so I'm removing everything and starting a new one. Let's hope that "Full Edit" hasn't been changed back to resurfacing threads...
Gonna hijack your thread because I am too lazy to make a new one. Just did it 5 minutes ago and it worked.
From CheapAssGamer forum
Sign up to get a free Thief Gold Edition Steam Code.
Note: The Code you get from signing up does not give you the Steam Code. You have to go Amazon first, put Thief Gold into your Cart, and once you reach the Payment Screen, put in the Code you previously got into the Promotion Bar. And viola. You should get a free code.