I think that so much of the success of any of this is personality, or personal character driven. The policy is not necessarily at fault but the wack job participants.
I'm sure mature, honest, self aware, loving adults can handle these arrangements. And conversely insecure and immature idiots will fuck it up.
From the example RP gave how does someone in a declared "open marriage" with a stated DADT policy in place flip out when it's discovered that other relationships are actually happening. Then on top of that flip out on the outsider???? Nothing makes sense in that. Sounds more like go ahead have a relationship as long as I don't catch you. How young were these people?
Then to call you up a yr later and want to hire you for a 3some ...some fucking balls.... or wack job