Agreed, at least where, as you indicate, in practice it’s really “polygyny” (another new term for me!). Not sure who would ‘howl’ at calling that oppressive? This was the gist of my last paragraph above, and why I hypothesized the mythical ugly Mormon guy. (None of the Romneys would seem at risk here.)
I suppose if the rules were applied symmetrically, the social implications of polygamy vs. polyamory wouldn’t be too different. Perhaps fear of commitment = fewer such relationships.

“In short while your sex life is really none of my business, that may not be true with your marriage.”

This is where I asked sincerely (of anyone) what the difference is between marriage and civil union? Is it all about the tax break? Please advise. Again, it seems obvious to me people should be able to bequeath etc. their *own* assets as they see fit – to your point about contracts and common law. But if we’re talking about who has a coercive claim on the assets of *others* (i.e. taxpayers), that seems like an issue which at a minimum people get to vote on. Is their more to your reference to “the community”? And again I qualify all of this with a preference for using the tax code to raise needed revenue in the least destructive way, and not for endorsing certain types of relationships.

First there is the practical aspect. Polygamy, as widely practiced in the world, is accompanied by rules that make the whole thing tough on women. It will be difficult to deal with this in our society if we simply legalize polygamy, which will essentially mean legalizing a certain kind of oppressive polygyny. (Can you hear the howls yet?)

On a theoretical level, marriage involves the community and common law in ways sex alone does not. Maybe not in some imaginary libertarian future, but in society as it is now, everywhere in the world, this is true. Enforcing contracts, presumptions of privilege, etc. So the considerations for messing with it are different. (More howls.) In short while your sex life is really none of my business, that may not be true with your marriage. [Please not I have not stated my opinion either way.]

I think n.r’s argument is a lot stronger applied to polygamy.

We might agree on examples of net social burdens we should tolerate (a distinctly non-utilitarian position?), but I’m not sure we’ve established any yet…and the question on the table was, is polyamory one of them?

- Free speech – clearly we believe this is a net social plus (and personally I don’t worry much about ‘offensive’ words but actions, which are punishable; in fact this blog proves that I can derive the most entertainment value from statements I may find objectionable, as they stimulate the discussion).

- Smoking at home – I presume this is about the health care costs = burden-we-choose-to-impose-on-ourselves (which came up on a recent post).

- Polyamory – I agree nobody.really articulated the case as well as could be, but my question remains do we think having kids under those circumstances is really net negative, or just less positive than if the parents made all of our preferred lifestyle choices – i.e. the difference between taking your $5 or giving you $5 instead of $10.
I’d add that it could be most of the search costs are in finding the one stable mate who shares in the child-raising, and from there the costs diminish. Also IMHO kids are more resilient than we often give them credit for. Most of us can probably think of things our parents did that we vowed not to emulate. Lots of influences out there, and it takes a village right?

BTW nobody.really also proposed an interesting (if indelicate) negative channel sans kids – “To be blunt, the norm of monogamy may have evolved to promote social stability by helping otherwise undesirable guys get laid.” A stronger argument for legalizing prostitution? And there will always be unattractive women too, so couldn’t polyamory simply increase the options within all strata of ‘desirability? The presumption here seems to be that desirability is less important and frequency more important for males than females. (‘To be blunt, barring any social stigma desirable guys will nail anyone in sight so the undesirable women won’t need it from the undesirable guys.’) All of which may be true. Makes me really wonder how ugly Mormon guys survived back in the day.

KenB: Let me see if I understand your reasoning here.

1. Sierra supports the abolition of the legal definition of marriage that restricts it to being between a single man and a single woman.
2. Therefore, Sierra supports the abolition of heterosexual, monogamous marriage.
3. Therefore, Sierra has a problem with anyone having a committed, heterosexual, monogamous relationship.

So a claim about what Sierra said, and about an alleged trail of reasoning I based on it.
But of course as I have pointed out repeatedly Sierra said she wanted the abolition of legal marriage, which is nothing like Rowan’s point 1. The whole thing is just Rowan’s confusion and confabulation foisted upon me, baselessly.