It's to be a collection of YA (Young Adult) romance stories.
One story, by author Jessica Verday, was accepted -- and then sent back with instructions to change her male-male protagonists to male-female, because the publisher wouldn't accept a male-male story.
Then it came out (pun only partially intended) that the publisher had said no such thing, it was entirely the editor's opinion.
Then the publishers "regretted the misunderstanding" but "stood by" the editor.
And so Seanan and other authors, in the interests of not supporting discrimination and bullying, have pulled their stories as well. For more details, you can read Seanan's post on the matter.
This is a risky choice for an author, even one who has mad as large a splash as Seanan. She loses the pay for this story with this publisher, she potentially burns a bridge to this publisher for the future, and she risks burning bridges to other publishers as well (because editors and publishers talk to each other, you know).
But I think it's a right choice and a right action, and I wanted to share my respect for Seanan with you. I already respected her, you understand, as an outstanding writer, delightful LJ poster, and all-around nifty person I'd really like to meet some day, but this has just impressed me all the more.