A while back there was a concept for a captcha I liked, but it seemed to vanish. It was called something like "StupidFilter" and asked a free form question. If you answer the question correctly, you can then post data on the site. That doesn't seem complicated to me and if each site had their own unique set of questions it might be harder to make a generic bot to bypass it. The reason I like this method is that you can tailor it to the audience of your site. PC modding site? Have entry-level PC modding questions. Bots would have to become domain content aware. Not perfect, but I don't need perfect.

Asking the web developers on here, how difficult would it be to make something like that? Or does that already exist?