In an interview on NPR, the lead writer of the paper explained that while there's no shortage of banks willing to process spammers' transactions, they can take

In an interview on NPR, the lead writer of the paper explained that while there's no shortage of banks willing to process spammers' transactions, they can take down a merchant account in a matter of hours but it takes days to set a new one up so, at least right now, the advantage would go to the defense. (If banks make setting up new merchant credentials near frictionless then we're back to square one. And we know we can't do anything about banks.)