The App Store for iOS is very prudish, or not. Bang with Friends is not prudish at all. It's stated aim is to get its users a one night stand (that's a euphemism for sex at no cost) with Facebook friends. Get it? Bang with Friends. But Apple doesn't like the name. Can live with the intention, but not the name. Go figure.
Bang With Friends (BWF) is a sex app that allows users to anonymously hook up with their Facebook friends. And yes, this particular app is on fire as its popularity quickly increases.