From the lips of a pet:
open relationships have to be based on complete trust, much like faith in a higher power, you do not get "in your face" proof of the mighty existence- or hard proof of partner trust. One will never be quite sure that, after all the pets have gone home, that their lover's thoughts belong to them. a true open relationship does not need to give or get consent, when choosing sexual partners; as long as no STD or extra kids are brought home. This is actually the troublesome type of relationship, unless you really don't give two hoots who has been dipping fingers in your pie.

The relationship status that harmony is referring to is "poly" -polyamerious (i know i did not spell that right) , one lover and many playmates. This type of relationship is more one sided, having one dominate(leader) partner and one follower(lover). The dominate partner cannot help but be attracted to others, the lover attempts to understand and thus agrees to "play-dates" where the lover literally gets to approve of the playmates. It shows respect from leader to lover, the leader trusts the lover to pick, and the lover trust the leader to come home again.

Our "family's" (wife/husband/me) "playmate shopping" would consist of going to various clubs and learning what each other liked about others. things like, hair style, jaw lines, eye color, body build etc. with this information we could then pick playmates that would please our "leaders" without making our "lovers" feel insecure.
At the end of the day in a poly relationship, it is all about coming home to the one you love the most,and being there when they need you, even if it means leaving the hot piece of "candy" and the bar alone.