I would never be in one. I rather be single.
A guy that i've been with (not exactly a boy, a man since he's 30

) asked me if i wanted to be his boyfriend but only if we had a open relationship. I said no. He always had open relationships and believes in that, but honestly for me it would be just a way for someone to cheat on me and not feel guilty for it. I wouldn't accept that.
I'm not mature enough to handle it, but i don't really care or judge if someone out there do it. Their lives, their relationships.
I'm far from being conservative or else but this is something i can't deal with.