Also,

It seems strange that users would be willing to sign up and pay for a service at a file host, committing themselves and their money to that service, but not to a payment system that may require only a few cents to try out.

CarrotPay does not store any personal information, and as users can 'top-up' and withdraw by/to paypal, it seems to me that they have little to risk.

Conversley, if a downloader wanted to sign up to a file host subscription, they would risk all the money the put in, and make a commitment to that service and lose all funds regardless of weather or not they use it.