1) Of the body of fic that you've read during your time in fandom, roughly what percentage includes sex scenes, and how many of those scenes contribute to plot advancement or character development?
I came to LJ for the smut and stayed for the angst. The first time I googled House/Wilson slash, it took me to house_slash and I spent three months glued to my chair at work, feeling like a character in a smut-fic, reading the whole archive, and was deliberately reading the smut, so that reading still skews my statistics. Let's say at least 65-70 percent containing the sex and 45-50 plot advancement/development.
2) If you're an author, do you ever include sex scenes in your stories? If so (and please be honest), do you always do it strictly to advance your plot? Or do you sometimes do it because it's what your readers want/expect you to write?
YUP! From the first fic I ever posted. It's what I was reading and what I wanted to write. I do write smut to make the readers happy, but not because it's "expected." When I've taken on a specxific request for gift-fic, I've usually made it hard-core, unless I feel the pairing won't support it.
3) Do you enjoy writing sex scenes? Or do you struggle for every word ...
The longer I do it, the (ahem) harder it gets, mostly because I'm more and more conscious of the potential for bad smut cliches and I'm usually trying to pre-Beta myself to avoid them. On the other hand, sometimes I still get carried away and it's like gliding over ice and I know immediately I've got a winner. Luckily I have beta_goddess and hllangel to talk me down when the evil smut cliche demon attacks without my knowing.
4) Do you believe in your heart of hearts that most romantic stories should include sex?
I don't write a lot of "romantic" stories. The pairings I'm drawn to writing about aren't particularly lovey dovey, so they're far more likely to have sex than long walks on the beach. I only have one pairing that includes both. Those are my Hugh/Bobby RPS and that relationship (in my 'verse) is still driven by the sex. If I were writing a more conventional romantic couple, it might be possible, but there'd have to be some other major conflict to drive the story. So if you're talking about pairing that I consider angsty hot and you're writing a schmoopy romantic story about them AND completely leaving out the sex...we're going to have a problem.
5) If you read a story with strong sexual overtones, do you feel cheated if the author does a fade to black? Why or why not?
Assuming the writer has rated and summarized properly, I should know what I'm getting into. If they somehow promise more than they deliver, I might feel cheated and would probably comment with a groveling plea for someting hotter.
6) If you're an author, do you feel a subtle pressure to write smut even if you aren't really comfortable with it?
I'm completely comfortable with it. But no, I don't feel any pressure. On the other hand, I think I'm providing my readers