I've been wondering. Can't Badspot forbid payments from particular paypal accounts for those that are revoke-on-sight?
Not sure if that's a feature of PayPal, but it might be.
If it is though, he'd only be able to deny a purchase when someone buys it from Blockland.us.
And they could just buy it through Steam, where you don't need PayPal, you just make a payment straight from a debit/credit card, or through Steam Wallet cards.