> I think that someone who doesn't want to give their real email address to try out a service is even less likely to trust an unknown service with their credit

> I think that someone who doesn't want to give their real email address to try out a service is even less likely to trust an unknown service with their credit card number. And that's OK. The problem as I understand it is that people are signing up with disposable email addresses, using the API key they receive for 7 days, and then signing up again. They are leeches, exploiting the generous free trial. If they stop signing up, no problem. Other people who sign up with a disposable email address can test within the restrictions, and once they trust the service have a choice to enter card details or not. If they are planning to do business with the service, they're going to have to trust it with card details.