I suppose it's kind of appropriate, isn't it? As a splicer, you're supposed to have been driven insane by the use of plasmids and what's more insane than a little teabagging?
And I'd have thought that Big Daddies would be like the Jedi in Star Wars: Battlefront 2, where you just randomly get one at certain spawns and everybody else tries to kill you instead of each other.
Having said that, I probably won't be using multiplayer. Would if I could, but my wireless connection is just that little bit too far from my tv, and I can't afford a booster.
/cry
I agree though, that I can't see it being anywhere near as rich in setting and story as the single player would be.