Competition with friends
Learning a new language is something you do .. for your own good. You're not obligated to prove to anybody that you can do it. It's not something to be boastful about (though you can of course be proud of it).
Having said that: The leaderboard motivates me more than anything. Especially when a friend is learning the same language and is on par with me. Currently, however, the only competitive element is the mail saying 'Friend A has passed you on duolingo' - and the leaderboard of course.
Let's say both users consent to it, would it be possible to have some other form of comparing scores? E.g. my friend has learned X words, my friend did Y lessons on these days while I only did Z, etc.
I think that the gamification aspect of duolingo is one of the features that makes it so successful, and (to me) it feels like some competition would add to the 'game' of learning language.
If it was optional add-on. If it wasn't, I'd rather stick with the way things are now. ^_^
Agreed. It may work motivating for some, but not everyone has a need to have their skills ranked or compared. Both users should agree to have these 'duels' (or something sounding less aggressive) beforehand.