Can The Open Source Model Work For Textbooks?

Paul Maud'Dib asks: "My mother is both a teacher at a local college as well as a writer for a major textbook publisher. She has spent the last four years writing, reviewing, rewriting, sending out for reviews, rewriting again, shifting focus, and then a little more rewriting. Unfortunately, she was paired with a cowriter that had good ideas but lacked the ambition to fulfill her part of the project, leaving my mother to write practically the entire book herself. These kinds of problems--review, rewriting, collaboration--as well as the general purpose of such a book (not to make money, but for education) seem to fit quite well into the OSS development model. Not to mention the $500+ most college students would save given such a model. Yet very few, if any, real textbooks have been developed and published in such a manner. What barriers, if any, prevent such publishing and what should be done to stimulate the OSS model in textbook publishing?"