From reading the sign-up page, it sounds like each month you are billed you receive a 'credit' that can be used to purchase an item from the site.

To me, the responsible thing to do would send an email to customers that have been billed for the month but have no yet redeemed their credit near the end of the month. Let them know they have a credit and suggest some items that they could purchase with the credit.

At least that would give information to the customer so they are more aware of what's going on sooner rather than later and people may feel less that they are being 'scammed' because the site was actually trying to help them get what they are paying for.

However, I agree that the signup page should make it more clear that it's a recurring charge. In fact, I would support a rule/regulation that required a user check a box that specifically states, "I understand that I am agreeing to a recurring monthly charge of $xx.xx".

I know that I'd be pretty pissed if I saw a recurring charge show up that I wasn't expecting.