Ugh, a used to have weekly afternoon play dates with a hot guy who wanted to do that to me. He stopped when I asked him to, but I wonder why he wouldn't have cleared it with me first? It really really really turned me off. This was in the early 2000s, by the way, and I have no idea if he got it from porn, but I suspect the concept didn't occur to him out of nowhere. But yeah, for the record, please don't spit in people's mouths without asking. (Odd I should feel the need to type that!)