The idea behind groupon is to make it easy (and cheaper) for new customers to try out a service or product. The whole site really looks like racket but I used it some time ago. I have the common practice that I create an e-mail address for every single service I register to. So I used an e-mail address of the style "email@example.com" for it. Today I got an e-mail with the subject "Abmahnung Ihrer aussehender Rechnung über 262,00 Euro" (impolite german for "Reminder for a payment about 262 euros") from an debt collecting agency. Do you want to know more?