Open relationships...why?

Can open relationships work? Even if you love the person? Why would you enter into one?

So what's sparked this thought today was a conversation I had with a friend, who, despite having a boyfriend, they have decided to be in an open relationship as neither of them are in the same country and they would need to fulfil their sexual needs. They have both agreed to sleep with other people, whilst still claiming to one another.

In all honesty, I find the idea of an open relationship wrong. I have been cheated on twice and so I am automatically against the idea of my boyfriend actively sleeping with someone else whilst being with me. Not only that, but I am in a happy and secure relationship. I cannot imagine myself sleeping with anyone else but my boyfriend because I love him so much, and with anyone else it would be the ultimate form of disrespect and if I ever did that, I'm not even sure I would even forgive myself. But for me, sex is a big deal, I associate sex with love and always have done, and the thought that you can still love someone and then have sex with someone else is something which I would never understand.

So I wanted to get your opinions. Can you really separate sex from love? If you are in an open relationship, do you actually love the other person? and as I mentioned before, why are you in an open relationship?