Coupons are meant to build customer loyalty. Of course the scheme can backfire. Let me give you an example
I have purchased all sorts of things from Vistaprint.com . Now I am a pretty loyal customer, and don't browse around for a cheaper price at a competitors site. Or at least till a recent incident.
Visaprint sent me a coupon for 15% off. I was going to order thank you cards that week, so I was glad I got the coupon. As I am about to press the submit button on the order, I decided to check and see if there are any other internet coupon out there for the site. I found one with a simple google search - a 50% off coupon! 50% for everyone vs. 15% for your loyal customers? So a first time customer is as good as one that generates an order every three months or so? Now I would certainly shop around at other print sites before ordering
Lesson of the story: be careful what sort of orders are floating around, before you award your loyal customers.
P.S. As I pressed publish on this post, I saw another coupon for Visaprint on my confirmation page - 90% sitewide!