That’s what I call a win-win. From BBC World Service 20/06/12: Duolingo, aims to translate the entire web with the help of people starting to learn a new language. It's a project born out of guilt from the man behind one of the most annoying features of web surfing - those online security checks involving random words. Duolingo hopes to convince millions of people to work for free and thus translate all web content in a matter of years. As a 22-year-old graduate student in 2000, von Ahn invented the Captcha - those distorted images of words and numbers used to sign in to ticketing and social media websites, among others, which users have to decipher to prove they are human. Erm, and to leave comments on blogs!

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