When helping my Dad to set up a Gmail account, the CAPTCHA kept rebooting us over and over, back to the form, where we had to resubmit the password and password confirmation. (Ugh.)
I thought at first it was because of his poor eyesight, so I then took over. Well, it took *me* four times to get the CAPTCHA right, and I think I’m fairly human! CAPTCHA’s have got to change. Thanks for bringing this to the spotlight.
Interesting article that I wholeheartedly agree with.
I think the addition of a CAPTCHA is something that should be weighed against what you are trying to achieve. The CAPTCHA is simply an obstacle and any can be circumvented simply by employing human sweatshop relay attacks. Decide how viscious you need your CAPTCHA to be and then choose a solution.
For example, for me I use reCaptcha when I want something pretty foolproof. When I don’t need that kind of protection, I created a service from http://textcaptcha.com to generate random questions. These are less secure, but easier to deal with.
The question of how big an obstacle you need is an important one.