For me this is an interesting question. I didn't curse when I was a teenager. I don't think I would have cared either way reading it in a book; I mean, all my friends cursed so it's not like I wasn't aware of it. I was the oddball (as always, lol).
For one reason or another, I started cursing. I don't really know what happened, I think maybe I wanted to be cooler, or express myself better when I'm angry. (Saying "darn it" just doesn't have the same emphasis.) I don't think of myself as the biggest curser ever, but I definitely don't shy away from it. At. All.
But I don't curse in my novels. Maybe I'm trying to hold on to my childhood, I don't really know. But I just don't really think it's the right place for it, in my novels. It just doesn't go with the tone of my my stories. But I'm not at all against it for other young adult novels, because the fact of the matter is they hear it all the time anyways. They're going to make their own decisions about whether or not they want to curse.
But the thing with profanity is that it's kind of lost it's meaning. People drop the F-bomb all the time over things that don't really matter. [Myself included.] And that's kind of a problem because these words do have power behind them. Teenagers might say "eff off" and not really mean it as anything, and that's a problem. Someone could react to that like it's no big deal, while others may be very hurt by it. And we have to respect everyone's reactions and understand that they may differ from your reactions. I think that's what we should really teach teenagers. We shouldn't just ban books because there is cursing in it. Again, they have heard it all before, so it's not like we would be introducing anything new. We need to teach teenagers that their words can hurt, and that everyone reacts differently to cursing, whether it's being offended or not. And while to me, it's fine for teenagers to curse, they also need to learn how to be respectful, and I don't think banning books because they have profanity is the way to do it.