Team up with duolingo! (or do a similar approach)
This is probably one of the best language learning sites I've ran into. I couldn't find a single thing to complain about, and then I noticed something. Some features cost money, and I get it. You guys need money to maintain this site, but charging money from it's users would only hinder it.
I'm sure you've guys have heard of duolingo. It one of the most well known language learning tools out there. Why? Because it's free!! Users on duolingo provide a service by translating the internet while learning a language for free. Everybody wins! I was thinking either you guys could try a similar approach, or try to contact Luis van Ahn (the creator) and team up! You could offer some tools that duolingo doesn't have (like your spaced repetition cards and definitions) and in return, you'd receive some of the money that duolingo gets for it's translations. Just an idea. :)
They are working right now with Duolingo. Yeah !!!
Maybe they could also work with Bliu Bliu or Lang8 in the future I hope! But I guess they're already busy with this wonderful site Duolingo.