I think the core of the rape fantasy is about permission. Our society is largely repressive of the sexual woman: she is a "slut," which any high schooler will tell you is about the worst thing in the world. So rape -- in concept -- is being given permission to enact any perversion by being forced. Without assent, one can't be a slut; but one can still enjoy all those pleasures and desires! The key to the idea, though, is that it's PERMISSION -- that is, it's what the girl wanted all along. Real rape isn't like that: it's being forced to do something she doesn't want, and is therefore completely and absolutely opposed to the rape fantasy. Anyways, just my 2 cents.