I'm actually kind of amazed to see this subject brought up at Wendy's blog because it is so ignored. Like Wendy, the women I know in real life are more diverse and more adventurous than the women/girls in romanceland. I haven't read a girl/girl scene in any kind of romance yet, though I heard that one of the Luna's has bisexual relationships, if not actual sex. Maybe The Compass Rose by Gail Dayton? I checked it out from the library, but haven't read it yet. And like Wendy, Emma Holly's Velvet Glove (which Candy said has a girl/girl scene) is now on the top of my list as well.
Oh, the excerpt from M. J. Rose's first book for Harlequin's Spice line is a girl/girl scene, so it seems Harlequin is going to be open to it.
In AAR's Demographic survey a few months ago, they had a sexuality question. Of nearly 700 respondents, 98% identified as straight, none as gay, and only 2% as bisexual. That's only 14 people. Which is probably low, because I'm sure there are some who lied (though I doubt it's low by a whole lot). I would also assume that if the idea that AAR's readership is more liberal than the general readership is true, then that would mean that there are very few bisexual women reading romance at all.
I think this is also partly a generational thing. Yeah, the 60s was the "free love" period and all, but it seems like the idea is that it was okay then, but not now, and only so much anyway. Younger generations (like mine and the up-and-coming) seem to have more freedom with sexual experimentation. Not sleeping around so much (though that's okay in many circles as well), but being open to other options and/or feelings for people that might once have been considered impossible.
I have read a couple of non-fiction books that were interesting: Odd Girls and Twilight Lovers: A History of Lesbian Life in Twentieth-Century America and Intimate Friends: Women who Loved Women 1778-1928. I'd love to see some historical authors tackle the issues brought up in these books.
It seems like bisexuality is in a way the "New Gay". Nobody talks about it, very little is written about it (and what little is written is about bisexual men) in either fiction or non-fiction. Romance writers (even the erotic ones) won't touch it. I'd love to see it dealt with more openly and fairly.