Here's an interesting post from Coding Horror. Basically, describing whether the CAPTCHA is broken or if designers are just using sloppy methods. What I find interesting is software utilities designed to "break" the CAPTCHA. Looking at that post, Google, Yahoo! and Hotmail have unbroken CAPTCHAs. So, if the CAPTCHA was broken, I guess my question would be, why would Google, Yahoo! and Hotmail be using them? Apparently, they know how to do it right. Google also shows that a CAPTCHA can be effective yet readable.
Anyway, interesting read. Thought I'd share. Being a programmer, I can appreciate the nature of that post.