I’ve used Duolingo for a little while and did appreciate the gamification to certain extent (I have a friend who now lives in a different country whose progress I could also follow and try to keep up with), but the repetitiveness (at the beginner levels) became annoying after a while. I understand the reason for the repetitiveness – it has to do with the forgetting curve and the software applies the concept of spaced repetition to get things into your long-term memory – but the choice of words to teach was poor. While the community of more advanced learners is quite good, I just couldn’t get into this program because I wasn’t learning things I could use right away (knowing how to say “Bear” in German or French may not be particularly helpful in a typical conversation).
In terms of Luis von Ahn as a role-model, I think I would have a hard time relating to him. His accomplishments are worthy of admiration, and he has clearly used his education and research to successfully tackle real-world problems. However, I see him more as an academic than an entrepreneur – his project’s “hidden agenda” of having humans translate things that are impossible for computers to translate seems to point to potentially more research data being generated for analysis.