Why Didn't Captcha Advertising Take Off?
dragonquest: One of the first problems I see is that supposing you are a webmaster of a site and 5 companies have approached you to display a fuzzed up logo in you captcha.Now since there aren't infinite string variations you are left with randomly displaying only 5 kinds of verification phrases which are easier to manipulate once you take into account that colors associated with brand logos are easier to recognize than actual alphanumeric strings displayed as images.Also since captcha's are mostly for the benefit of the website/webmaster, they are seen in an annoying light by consumers who actually use the site. And that is a strict no-no to any marketing strategy.