Note: The majority of this post is specifically referring to MF couples, although there are comparable dynamics in gay and bisexual relationships, and kink as well. Please feel free to fluidly play with gender and power play concepts in this piece!
The One Penis Policy: Where either member of an existing couple is open to connect physically and/or emotionally with an outside partner, as long as that partner is female. Fortunately, this isn't something that is a factor in my life at this point, but it is something that seems to be rather prevalent early on in many people's early poly/open relationship experiences. Why is this?
Here you are: A lovely couple who is affectionate and caring with each other. You talk, and talk, and talk about the idea of opening your relationship up, about having sex with other people, about connecting emotionally with those people. Why are "those people" almost always female when you are first exploring this concept? Is there an ingrained perception that women are safer physically? Safer emotionally? Is it purely a comfort zone issue for the man? For the woman? Is it an attempt to enforce female bisexuality in pursuit of the elusive unicorn/FMF experience?
This is where I have an issue with the OPP: It "weights" penises, and the men attached to them, as different than women. In fact, more points go to the men. It means pretty implicitly that women don't count as much as men do in the equation of sexuality. It says that there is more fear directed towards men in relationships, that they are a poor risk for trying to "steal" a partner, that the man in the existing relationship may be insecure about his value to his female partner when there's another man to stand (or lie!) side-by-side with. It plays into fears, without establishing if they are unfounded, or person-specific, making a blanket judgement for an entire gender. It says that if you have an innie, you're safer than someone with an outie.
Now, I do understand (personally) that some women have had bad experiences with one or more men that cause them to be more cautious on a gender-based level. I'm going to suggest that that is a limit that there is great value in pushing past. Find a space where you see each person as an individual, rather than a representation of a bad experience, and THEN apply your keen observational skills to determine if this person is someone you'd like to connect with, regardless of their bits.
There's the ever-popular "But, she's bi, so it makes sense for us to find a woman to connect with, so that we can both date her!".
Potential dating partners are very seldom going to offer a one-stop-shop approach. Last time I checked, she was also into men, as she's with one already, right? She isn't likely to stop being interested in other men, even if she also likes women. So, why try to force things to fit just a single gender?
Maybe it's the penis cooties? Since most of us engage in safer sex, I fail to see how any woman's vagina is going to be sullied by insertion of an additional latex-enclosed penis. Even in a situation of being fluid-bonded to more than one man, basic hygiene observance takes care of that concern.
Even if a woman is in a space where she isn't interested in adding more masculine energy to her life currently, that option belongs on the table, not in the Forbidden Zone. It's about choices, and having them available to say "no" to, if that's what is appropriate for the individuals involved. Do away with the OPP!