I'm very happy with Duolingo because I have improved my skills in languages such as english and portuguese. However, I think Duolingo should to create an option that let us translating videos and putting subtitles in any language. In this manner, we can improve the listening skills without losing the sense of translation.
I really agree with this idea, since I know what it's like to be "fluent" in a language without being able to really understand it.
Just an idea: Perhaps it would be best if we could choose a video we want to translate early on/ahead of time, and Duolingo could analyze it, and then customize new vocabulary based upon it. I have found that many times the biggest impediment isn't "lack of vocabulary", but rather "lack of vocabulary in context". AFAIK, YouTube offers captions as part of their API, so for the most part Duolingo would just need to compare that to whatever vocab you already have, and go from there. :)