I haven't used the site. I would be wary of using a site that required your giving them your credit card info when you didn't have to actually pay for anything on the site. The excuse that it is needed to verify that you are from the US sounds like just that--an excuse to get your info.
It may be legit. If others have used it and had no problems, I hope they let you know.
Yup! I personally wouldn't touch a site like this.