I'm not sure if, in a post-Fifty Shades world, we can afford to be that insular. That book is decidedly not OK with the BDSM sexuality of its, uh, hero, and yet it's being held up as a stunning success in the markets of kinky and erotic fiction. This makes me think that a lot of people are not finding us, don't know what other stuff is out there, or how to find it. That makes me incredibly sad.
The frenzy over Fifty Shades is bewildering to me. As people have commented before, Fifty Shades is not the first erotic book aimed at women to sell a boatload of copies (see, for example, Nancy Friday's My Secret Garden, and, um, the entire Harlequin catalog). To some degree, I think this is a media event -- people at various media outlets feel they have to follow each other writing articles about the inexplicable success of this sex book (sarcasm here), and that feeds more articles and more sales. Why this book? Who knows? -- it happens that way sometimes.
But is erotica insular? I do think things that are specifically erotica concentrate in small press editions, dark corners of bookstores, and e-book publishers who of necessity market to the tech-savvy. A big thing Fifty Shades has going for it is massive publisher support, cross-platform availability, displays in stores including the supermarket, and so on.
If Fifty Shades encourages more mainstream publishers to get into more erotica, that'll be good, I think. It might pull the erotica section out of those dark corners.
I think there's also a packaging issue going on -- Fifty Shades doesn't have a red cover on it, or a picture of a shirtless man, and I think some of the shock is that the book sells anyway. But this is part of a larger trend that's already been happening. Harlequin has its Luna line, which is fantasy romance. A lot of fantasy books for a lot of years have been full of explicit, erotic scenes, BDSM included (see, for example, Jacqueline Carey or Terry Goodkind). I respect Fifty Shades' sales, but it doesn't really seem unique to me. Sexy books have been selling well for quite some time, I think it's just that a lot of the world didn't realize what was going on.
I'm holding out hope that this will increase people's willingness to go looking for the erotica tag, rather than sticking to books that have a lot of sex but are being marketed primarily as something else (say, fantasy).