I have never understood the hang ups around screen nudity (though it seems to be much more of a thing in America than here in the UK), but as a teenager, such scenes tended to provoke a revered hush from yours truly rather than snickering (whilst obviously noting the imagery for, er, future reference - I'm still flesh and blood, after all). Then again, I watched all films with revered hush. Considering I bleed celluloid, this is hardly surprising. I was a bit "special" as a child (I couldn't understand why my fellow eleven year olds weren't riveted by the films of Andrei Tarkovsky, for instance).

Also (perhaps weirdly, considering both my parents were quite strict evangelical Christians) I never minded watching sex scenes with them either. I remember on one occasion my mother questioned whether the nudity in a particular film was necessary. I just replied: "Why not? Breasts are beautiful." And my Dad guffawed. Other than that, we never discussed it. :)