While it's a quite interesting coding task to write a classifier, for the overwhelming majority of applications you simply don't need to know a user's gender. Making it a public API is a bad thing.<p>Developers have a horrible tendency to gather as much data on someone as possible, everything they're willing to give in fact, for the simple reason of "just in case we need it later". It's far, <i>far</i> better to gather as little as possible and build something that simply doesn't need to know specifics. If we build things that are ambiguous, unspecific for age, gender, race, nationality, etc then the world will be a better and more inclusive place. Paradoxical as it seems, more privacy actually leads to a more integrated society. That is universally a good thing (in my opinion, obv.).