This is completely useless as a solution to the captcha problem. It's only a solution if you're not actually tagetted by spammers.<p>A slider? Really? Yeah, there's no way a script could fake changing the value of a slider.
This (and other creative implementations) works because it's not mainstream. I'd imagine once it becomes big, spammers will find a way to defeat it.<p>As far as I know, different CAPTCHAs have different degrees of effectiveness. Google's is among one of the best.
Nice idea. No captcha would be better. How come Facebook doesn't need a captcha on their create account page? <a href="http://img.skitch.com/20100702-g2gt6pxcpyug324yhyay4gsj13.jpg" rel="nofollow">http://img.skitch.com/20100702-g2gt6pxcpyug324yhyay4gsj13.jp...</a>