^^ Good post, thanks.

Thought-provoking.
I think people should do what works for them. I think some people are more sexual than others, and some people develop attachments and jealousies differently than others. For me, I think I could have random sex with someone I felt connected to and not develop an attachment, if it was at a music festival or something and I wasn't going to keep seeing them (I have not tried this though). But I tend to develop attachments to people I have sex with and we end up in a relationship, because the reason we had sex in the first place was because we were attracted to each other in that way. And then I feel like I wouldn't want anyone else having sex with her, nor do I really want to do it with anyone else except maybe superficially sometimes, and that feeling is reciprocated. It seems that this feeling of "ownership" is common for people and always has been, probably a biological urge to form a family unit to best protect children, which are the result of sex except for recently we have the ability to pretty well control that. I know some people though for whom an open relationship works for them, and that's cool. I also know people who only have short-term sex, or even just have various people they like and have sex with when they're around, and never seem to form that attachment. Works for some people.
I also see a lot of people engaging in sexual practices that do not seem to work for them. Some people are promiscuous because they're trying to mask pain or trauma, and that is a bad thing for them. Some people are in monogamous relationships because they think they're supposed to be, and that's bad for them too. Ultimately, you should do what you feel is right for you, and doesn't hurt other people. Going around having unprotected sex with tons of strangers and spreading diseases is bad because it hurts yourself and others. Being responsible and having sex with lots of people could be totally fine, as long as you're not spreading disease and not hurting others (like, if you know someone is looking for monogamy but you do it with them anyway, knowing it will cause them pain).
I think this approach is a lot more sensible than following the words of people from thousands of years ago who were recording a system of social control, in fact THE BEST and most consistently used system of social control. We should do what makes us happy and feels right, as long as we're being honest about how it's really making us feel, and we aren't hurting anyone else.