It's been a while since I read this book, but I found it helpful as both a history of the development of folklore studies in the West and an exploration and critique of the notion of "authenticity" at the heart of the development of hte discipline. At the time I found myself a bit disappointed in her dismissal of the idea of "authenticity", but I think that she is correct in pointing out that we need to be aware that our own emotional need for this "authenticity" can be a stumbling block. This does not mean abandoning intellectual rigor, of course-- it is, for example, still important to understand the context of the piece under analysis, and I would argue that that includes context in time, origin, etc. Overall I find Bendix's argument well in line with the "new", or material philology of manuscript studies, in which the extant form of the text, rather than some hypothetical reconstructed form, is the subject of research and interpretation. I think this is a healthy development, and find myself more on the side of material philology, though I am certainly sympathetic with many of the goals of "traditional" philology-- a certain amount of "reconstructive ambition" is permisable I think.
In any case, I also find myself sympathetic with Bendix's arguments. I'll have to reread the book before I can give a more thorough treatment.