http://www.psychologytoday.com/blog/psyched/200805/why-do-women-have-erotic-rape-fantasies

These scientists hypothesize (among other things) that women have rape fantasies for SEXUAL BLAME AVOIDANCE, MASOCHISM, DESIREABILITY (that they are SO desireable, that men cannot resist them,) BRAINWASHING BY MALE RAPE CULTURE, BIOLOGICAL PREDISPOSITION TO SURRENDER, DESIRE TO "TAME THE HEART" OF THE RAPIST, etc.

NOTE: "...in most rape fantasies, the guy is a hunk, and the woman isn't terrified or disgusted."