Don't ask, don't tell.
There's an on-going debate as to whether "don't ask, don't tell" can be poly. On the one hand, polyamory is such a broad term that one can make it be anything desired, within their own mind, and a particular partner may be requesting to stay outside the flow of information. On the other hand, someone is out of the loop not being told, which will, in my opinion and experience, eventually lead to unethical behavior of some sort.
Disclosure is one of the foundation pieces in polyamory. It's so closely related to honesty and truthfulness that I'd venture to say that, without disclosure on some level, there is no polyamory. There can still be an "open relationship", but sharing with one's partners is one of the basic parts of the "amoury" segment of poly. Without the sharing of information, relationships live well below the available potential, no matter if they are mono or poly in nature.
As you may have gathered by reading some past material, my first significant poly relationship was poly on my side, and DADT on his. While his spouse knew of my existence, knew he visited, sent gifts to my child, etc, there was no capacity to be part of his daily life, meet any of their children, spend time in their home etc. It was one of the two major limiting factors that led to the demise of that relationship, the other being distance.
Without disclosure, the growth available in a given connection is truncated, on every side of the equation. Choosing to move into more active sharing of information can be challenging, particularly for the person that would rather pretend the whole thing doesn't exist, but knowledge of other relationships colors even the most skilled actor's responses, poisoning the whole system.
If one chooses to disallow DADT in their poly relationships, there may be some missed opportunities, but those are outweighed by the growth options that are no longer stifled by being in information restrictive structures. In short, "If you can't talk about it, you shouldn't do it."