It's a set up. They tell you that they need the credit card info to show that you're 18 yrs. Of age, however it's illegal to use a credit card to show age. Once they have the credit card numbers, they use them to sign you up with all kinds of other scam sites.
It is a scam to make them money through an affilaiate link, its such an easy scam too, you just need a fake profile and time, I only know this from reasearch into this kind of work.
