CAPTCHA is an acronym for “Completely Automated Public Turing test to tell Computers and Humans Apart.” A CAPTCHA is a challenge-response test that websites use to ensure that a response is not being generated by a computer.

For instance, Google has one on its Keywords Tool page. You can enter a search term but before you get any results, you must prove that you’re a living, breathing person by typing in a slightly distorted word or camouflaged letters and words.

The objective of using a CAPTCHA program from your point of view as an affiliate marketer would be to prevent computer-generated sign-ups to your opt-in list or computer generated sign-ups to your blog posts or computer generated entries to your guest book, etc.

With the enactment of the CANSPAM Act of 2003 you’ve probably gotten a bit more concerned about your opt-in list, especially. The penalties for SPAMMING are stiff and you want to be certain that those who opt-in to your list understand that they are, in fact, opting in.

You’ve probably gone to the double opt-in…most of us have. When a user opts-in your autoresponder sends an email and the user must confirm that he IS opting in by clicking a link in the email. The double opt-in works…no doubt about it. There’s also not much doubt that the double opt-in decreases subscriptions considerably.

Another option is the use of a CAPTCHA program in conjunction with your opt-in box. CAPTCHA prevents computer generated sign-ups but it also makes the user verify that he is opting in.

There are several free CAPTCHA programs available on the Internet.

Would the use of a CAPTCHA program provide an adequate defense if a user complained to the “authorities” about you SPAMMING them? We don’t know. The theory hasn’t yet been tested. But it is a thought worth considering since we all know that the “double opt-in” does dramatically reduce subscriptions.