If you want to pay for something anonymously on the internet, you can use a prepaid gift card. It will generally be accepted just like a credit card (though there do seem to be exceptions). It doesn't require registering your address or SSN. Or at least not in the case of Vanilla Visa (they require, IIRC, a name and zip code, but there's nothing preventing you from faking those). You can't refill it, so you'll have to keep paying for new ones if you intend to do it a lot, but I guess that's the price.