You hate when it happens but this scenario is all too familiar: A customer is ready to check out, spies the enticing "enter coupon code" box, then scurries off to Google only to return through an affiliate website with coupon in tow. It's a double-whammy. You're giving up margin for a coupon that wasn't earned and to the affiliate who is basically a middle man not offering much value. The equation just doesn't make sense.
What does make sense is rewarding customers with a coupon for a social action -- a share, a tweet, or a Like, etc.. These actions build your brand, drive new traffic, and ultimately sales. You also cut out the pointless affiliate pass-throughs.
We've made it simple to add promotions per sharing source (maybe tweets are worth more than emails for you, or a Like even).
After you've added a promotion, you can toggle on/off the promo callout (currently seeking patent protection) that's displayed next to the sharing button. This preempts customers who see the button to share for a coupon rather than leave on your cart page to search for one. We'd suggest leaving the promo callout on as it really does entice customers to click through.
We think you'll agree that rewarding customers for referals makes more sense than rewarding coupon aggregators for nothing.