I don't think it would be hard to regulate. At Godiva we have birthday coupons that activate the year after you set it (Ex: if you sign up today and your birthday is Dec 25, it won't work until 2014). Meaning, if you set your birthday, and it happens to be Jan 1st and then after you receive your coupon, you change it to Feb 1st, it's not going to work until Feb 1st 2014. People can subscribe and cancel with the same email account as many times as they want but they probably won't be able to redeem a birthday offer multiple times a year this way (unless they have multiple boxes with diff bdays in each).Â