the only way to prevent spam is charge appropriate money, I don't see other solutions. Thats why many company use credit card to verify users. But, with virtual cards, they have some ability to spam, but not so much.
If you charge enough, the spammers become valuable customers. Of course they tend to leave before that point, but you don't really care if they leave or stay; you make money either way.
If you charge enough, the spammers become valuable customers. Of course they tend to leave before that point, but you don't really care if they leave or stay; you make money either way.
Value for value.