Ideas: * One idea is to use the classic "Give us your credit card details first" approach. You allow people to create accounts but, once they go to send their

Ideas: * One idea is to use the classic "Give us your credit card details first" approach. You allow people to create accounts but, once they go to send their first free letter, you explain that "To protect against spam, we require that you confirm your credit card details. Your card will not be charged for this letter." It isn't optimal if what you want are signups but it would definitely decrease fraud. * What about using an IP address filter that prevents people using proxies or IPs from certain countries (Nigeria for example) from using the free service? * What about pretending to send the letters from Nigerian/certain IPs but not actually doing it? This way would allow you to see patterns: which IPs or IP blocks were abusing the service, which search terms you could automate for blocking, etc. Basically you send back a "Your letter has been sent!" response to the user but you don't actually do it. * What about requiring telephone confirmation of address info?