And there is the essence of the need for captchas ;) You need to scale, so you employ computers instead of people. Now you have to have computers run a reverse

And there is the essence of the need for captchas ;) You need to scale, so you employ computers instead of people. Now you have to have computers run a reverse turing test. Otherwise, it's much easier for spammers to scale as well. It's easy to cut down on spam if you don't accept any incoming mail.