The recent break up of a multi-million dollar coupon counterfeiting ring in Arizona undercovered the fact that a lot of unwitting consumers are out there buying coupons to offset their grocery bills. That's further proven by the numbers. In the Q2 2012 coupon update, Inmar reported a 20% increase in the submissions of counterfeit coupons (which includes many of the coupons bought and sold).
The good news is that there is a group of ethical couponers out there strongly encouraging shoppers to adhere to the coupons' stated terms, which means no copying and no buying or selling of coupons.
One of the leading voices is Jill Cataldo who's point-of-view is illustrated in this post from eariler this year: http://www.jillcataldo.com/ethics_photocopying.
Clearly, shoppers shouldn't buy or make copies of coupons. But why?
It's important to remember that the entire coupon system works as well as it does because the retailers, manufacturers and shoppers trust that everyone is following the rules. But the reason for these terms specifically is that coupons are an expense to the brands — an expense they're willing to pay in exchange for the shopper's purchase of their product — but an expense they need to be able to show a return for and manage closely.