I don't think bondage or BDSM are abusive in and of themselves. Many women like to feel overpowered and dominated by men during sex, and many men nowadays have this idea that women have no such sex drive or are much too fragile to be treated as such. That simply isn't true. However, in that the book portrays the female character as submissive in all aspects of her life, and as without her own sense of self, and as totally reliant and dependent upon ''Mr Grey'', the book does romanticize psychological dependency, does portray the woman as nothing but a toy or a sex object, and does emphasize the idea that women need a man to validate their existence.
In that regard, it is not healthy to emulate such a relationship, but I see no issue with sex being what people want it to be, and that-- the brash statement the book makes about what many womens' desires in bed really are -- is why it has sold so many copies.
It is liberating in that it gives women a platform to say ''yes, we want this from you, sexually'', but it is also oppressive in that it paints a picture of a woman totally devoid of her own sense of self. If the female character had been independent it would not be so dangerous as it is. But then, what do you expect from Twilight fan fiction? Have you ever seen Bella in the movies? She's utterly without her own thoughts!