Hmm, in my head, I model conversation as a game of who can get the mine the most "intimacy", if you will, while revealing the least about oneself. So risque topics are, as the adjective suggests, high risk, but also high reward. Correspondingly, small talk is a lot of low risk, low reward back-and-forth. You don't have to be intimate with a stranger, but you need to stick your neck out if you want to progress beyond…
Obviously, you need to have some sense of the other person, and whether they will respond well. But really, most human beings are decent. And those who aren't, mostly aren't worth knowing at all.