Rules are made to set boundaries and I think we all need boundaries to live with one another. However, rules and boundaries shouldn't be used to be oppressive to anyone's personal growth, be it spiritual, emotional, physical or otherwise. Rules greatly depend on the maturity of the individuals and hopefully we all (ideally) can set our own rules and boundries for our own betterment. Rules to live by have been around since the first creatures were upon the earth...certain behaviours were/weren't tolerated. That is fine to protect the greater good of the family, village, etc., so long as the rules are followed by all in the same manner. Unfortunately, interpretation of said rules varies from individual to individual. Toss in life experiences, good and bad, extenuating circumstances (physical or mental disabilities), etc., and said "rules" may not apply. Yes, I believe there need to be boundaries in poly per se, but nothing set in stone or so rigid it is ungiving...like a tree in the wind, the rules should bend with the way the wind blows. If the tree does not bend in the wind, it will break instead. So goes a poly relationship and it's rules...any relationship and rules in general.
Factor in the different individual's personalities, those with strong personalities may have more influence in setting the rules for poly...this just is not right. A relationship hopefully is ever growing and changing, so must the rules be ever growing and changing. What applies today will not apply tomorrow and what works with some individuals will not work with all individuals.
I suppose I prefer the term boundaries as opposed to rules simply because the term "rules" conotates one/some having power over another or others. Boundaries give us room to grow, rules do not. I'm all about growth; personal growth and growth in relationships.