I was pointing out the possible results of a specific set of moral, legal, and cultural arguments. Or to be more accurate, the demolition of them.

If there are many legal and financial benefits to being married, it's an incentive for a lot of people to figure out ways to convert their personal living situation into a "marriage." Maybe we're looking at it from the wrong direction, and should be phasing out the legal pedestals that conventional marriage has?

As I said, nobody is really thinking about it. Should a person legally be able to marry their brother? Sister? Two guys down the road? Why or why not? Is "marriage is a formal union between only two unrelated people" any less arbitrary than "marriage is a formal union between a man and a woman?"

Around the world, polygamy has just as long a cultural history as monogamy. Heck, it's all through the Bible with, as far as I know, no sign of holy disapproval.