Dont post codes openly in threads. Have people PM you for it and pick one randomly or something.
When you post a code in a open thread anyone can come by, see it and use it. Even if they dont have a CAG user name, just a google search will show it.
What are the Duke codes good for anyway? with the game delayed and all, are they still planning to release a demo with enough time to give first access to users with these codes?