And given that, an app to which people supply pictures with a certain expression and tell Facebook what expression this is very likely aims at getting training data for their machine learning algorithms.
@julianruf @Curator @aral my bad, I didn't read the original post. And you also provided plenty of sources to back that up.
I'd not stop with the sole purpose of training for generic emotions detection but it could also help them train a model for each user and then sell this model to ads and gov agencies.
What a great time to be alive.