Your Facebook Friends as CAPTCHAs
Traditional CAPTCHAs are often hard to solve and therefore Facebook is experimenting with social authentication where they’ll show you a few pictures of your friends and ask you to name the person in those photos.
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CAPTCHA Inventor Luis Ahn: Putting CAPTCHA system to Good Use
Dr Luis von Ahn invented CAPTCHA images that websites ask you to type to post a comment or send an email.
Cats Inside RapidShare CAPTCHA Images
The next time you download a file from RapidShare, you may be asked to solve a tough CAPTCHA image.
A CAPTCHA That May Be Very Hard to Break
The most interesting and hard to break CAPTCHA image so far..