My comment for Marriott_Guy is very simple: please enforce the rates at check-in. You'll solve the problem for all of us. If the front desk staff are going to let people abuse things like negotiated rate codes then they are meaningless. As you stated, legitimate users of the codes will be punished while the "sneaks" will benefit. If a rate code requires an ID or some other form of proof of eligibility, then please CHECK IT! The legitimate user won't have any problem with that at all, I assure you.