In conclusion, captchas are inaccessible, inconsiderate and frustrating. In addition, most captchas are not as secure as you would like to believe. A far more elegant solution is to use some sort of filtering system (like Akismet). Such a system can run behind the scenes and work without complicating the user experience.
It’s time to kill off captchas and stop punishing users for trying to interact with our sites.
via TimKadlec.com – Death to Captchas. I tend to agree, captchas create a cruddy user experience.