Hrm... If it really would end up being significantly one sided (regardless of which side it would end up as) then it would likely be bad. But the question is how one sided it would be. (I guess really the best way is to actually go around looking at poly relationships (not the cults, but actual freely formed poly relationships) and see what tends to happen on average.
A thought occurred to me today as I skimmed an article in a rationality forum where the subject of gay marriage cropped up; seeing as the issue has been hotly contested in various public fora and especially the courts, what about poly? After all, many if not all the arguments for gay marriage apply to poly marriage as well.
Questions for LWers who are currently in a such a relationship, or have an opinion to share:
Do polies want to marry each other or do such relationships not lend themselves to permanence above a threshold of partners? Should polies campaign for the right for a civil union anyway? what are the up and down sides of this? etc