The funny thing is, captchas aren't even necessary anymore. I've completely eliminated them from my employer's website using a free open-source jQuery plugin that still blocks virtually all 'bots. No "human tests" required.
Hmm, I've toyed around with the idea of writing a hub about my captcha removal experience. Maybe I'll go ahead and do it.
Captchas everywhere are awful. I often have to make twenty or more attempts before I get one right. They usually reduce me to tears. The spoken alternative is even worse. I have never managed to understand what is being said when I've tried to use it in place of having to work out what the distorted letters might be.