Not only do the women dress as if they were available for instant sex, the men all dress as rapists.
The male costumes I saw were all some variant of this: soldier, pimp, pirate, "savage," rapper, baller. Just about all the guys' costumes I saw that night were a version of "permitted to rape."
There's your party. The women all dress as prostitutes and serving girls. The men all dress as rapists. And then they get drunk and play it out.
"Play" is where it goes for most people, and i'm not suggesting that everyone who dresses up goofy and has too many drinks is going to end up as a crime scene. I still don't like it, though. You can have a lot of fun — and friends of mine did! — goofing around dressed as Borat or Log Lady or Cinderella or the Cookie Monster and enjoying the masquerade experience. If you're going to play out a rape fantasy, though, it might be a good idea to know that beforehand and know who's really down for that instead of just getting hammered and finding out.