While CAPTCHA’s are supposed to keep the evil spammers of the world at bay there is no doubt that they are an annoyance to the end user. Most involve deciphering a string of mangled characters in an image which you must get right before you can complete a transaction of some sort (e.g. for signing up to an email service or posting on a forum). Theoretically only humans can correctly identify the characters and hence proceed but in recent years many variations have been allegedly defeated by advanced optical character recognition software (check out this Chinese website which tells you how difficult each type is to crack and how much it costs to do so). It seems to have turned into a game of…