Serious question by someone who's not into this kind of stats too much:
What would happen if you took a big set of Facebook profiles and train some (the same if you wanna) CNN to classify picture->f for each f in profile features. Sure, for some features, your model should be able to deliver decent precision.
Does this mean that you quickly found out what features can be predicted from pictures & how well your CNN performs on that? Or is it possible that you just train models from picture->X where X is basically meaningless but significantly correlated with some feature because of the effect portrait in xkcd's "Significant" (Scientists investigate!) [1]