Bear with me on this one, because its definitely not what you're thinking about. Well maybe it is, but get your mind out of the gutter for just a few minutes.
I was perusing one of the many blogs I have bookmarked/listed on my profile, called "Rule of Three", when I came across a very interesting post called "Sexual Tension". In it, it basically describe how tough it is to write it and what kind of fine line you have to tread in the process.
I basically agree with the writer of the post, plus the commenters as well, that it's a very fine line in writing sex scenes. To be honest with everyone here, most (if not all) of my writing, has varying degrees of sexual content in them. It's what I'm most comfortable in writing, and I feel it's the easiest thing for me to write, besides dialogue. Go into too much detail, and you'll find yourself losing a good chunk of your reading audience, unless writing erotica is your bag. Too little, and you could lose a smaller chunk, unless writing family values/Christian books is your bag.
The only thing that I would beg to differ about, is that is should always move the plot along. I don't think that is an absolute hard and fast rule. I have written instances in which it does absolutely nothing to move the plot along, only acting as a very brief interruption to the moment. I think it completely depends on the situation you're writing about, whether or not the scene should move the plot along.
What is your take on this? In the type of genre you write/read, do you prefer one end of the spectrum to the other? Or do you fall somewhere in between? Do you think its an absolute that any kind of sexual scene, no matter how intense or mild, should move the plot along? Or do you find a shade of gray within this absolute?
I truly would like to know what your views are. I think it could help me greatly in what I write and how I write, in what the preference is out there. I'm trying to find the proper niche for myself and my writing, and this will go a long way in determining what road I should travel.