Learning a language is such a large, long term undertaking that I appreciate how Duolingo tries to use a few tricks to keep people on-track. It's also one of those areas where interests and incentives (maximising the time on app; regular usage) are rather aligned.

However after getting halfway into their Chinese course I feel quite disillusioned with their approach and actual content. You'd think an app with their market presence would have some amazing teaching strategies... but they don't. You can get through half of the course and still not know how to count past four. There's also lots of cultural context and finer points that are simply missing.

Anyway, I'd be curious to see how a more community-driven approach could play out, any whether it would lead to better content.