Aside from being annoying, does CAPTCHA really serve a useful purpose? When you fill out a CAPTCHA, you're essentially telling the website that you're a human being capable of reading (or in some cases hearing) the distorted word, phrase, or random characters. This is one method site administrators use to keep spammers from flooding the site with unwanted content.
Unfortunately, spammers have found ways around CAPTCHA. One popular method is hiring a team of people in another country to solve the CAPTCHA barriers for the spamming system. They are presented with a new CAPTCHA every time their system comes across one. Once solved, they move on to the next while the spam gets sent to the site automatically.
With this in mind, there are many useful alternatives to CAPTCHA out there. If your site is built on WordPress, you may find a solution in plug-ins such as Akismet, Challenge, and others.
Feel free to give your take on this question here:http://lockergnome.net/questions/125624/captcha-what-it-s-really-used-for
What do you think? Are CAPTCHAs still among the better anti-spam systems available? Is there something better?