While spam's a huge problem, and I'd love to make spammers pay, any decent email admin can tell you about spammers' 24/7 attempts to break into legit users' email accounts, and what happens when they do. Any sort of "pay to spam" system has to cope with that - on the technical side, on the payment processing side, and on the "you are helping them steal granny's money!" customer service side.
While spam's a huge problem, and I'd love to make spammers pay, any decent email admin can tell you about spammers' 24/7 attempts to break into legit users' email accounts, and what happens when they do. Any sort of "pay to spam" system has to cope with that - on the technical side, on the payment processing side, and on the "you are helping them steal granny's money!" customer service side.