I feel like it's for some people and not others. I haven't participated in one yet, but my boyfriend has always wanted to. He says he's even open to a devil's threesome (two guys and a girl). I think if I was fairly drunk, I wouldn't mind much, but it's the thought of my boyfriend kissing/touching/feeling up another girl that really doesn't sit well with me. And for that reason, I tell him that I don't want to do a threesome.

I mean, I know quite a few hot girls who I'd be fine with doing stuff with, even though I'm completely straight, but I will get SUPER jealous if my boyfriend touches another girl XD

You don't have to be bi to want to do a three way. I've never done it, but I know people that have. They say it's great.