Here is a TED talk with the creator of Duolingo, Luis von Ahn (he also built reCAPTCHA): http://www.ted.com/talks/luis_von_ahn_massive_scale_online_collaboratio

Here is a TED talk with the creator of Duolingo, Luis von Ahn (he also built reCAPTCHA): http://www.ted.com/talks/luis_von_ahn_massive_scale_online_collaboration.html http://www.ted.com/talks/luis_von_ahn_massive_scale_online_c...