Help do real scientific work in your free time! This app lets me fiddle with my phone while on public transportation in a way that actually contributes to our understanding of the lunar surface, making it a guilt-free alternative to launching enraged avians at swine.
Easy citizen science! Citizen science made fun and convenient. I'm much more likely to pull out my phone to contribute to Moon Mappers during a moment of spare time than I would be to pull out the laptop for the same reason. Earning badges gives it a competitive feel, which is just icing on the cake to knowing that you're contributing to real science.
Too small It's good to do citizen science on the go. But the pictures are tiny - we even on a Samsung Note 2!
Citizen science It's a good way to get my astronomy fix in at any time. Plus you're helping to do real research as well. Good stuff.