I think monogamy has value, particularly for providing a stable environment for raising children, but I've also begun to think it's overrated as well.

One thing I find incredibly interesting is seeing what the bible has to say on the subject, since that's widely believed to be the source of the moral outrage at non-monogamy. As it turns out, the bible says remarkably little about it, and never explicitly states that monogamy is the only moral sexual relationship.

In fact, I am confident that the bible does not say that sex is only legitimate within the bounds of marriage (though I'm sure modern christians will label me a heretic for saying as much). It does condemn adultery, which makes sense: one should honor his commitments; it points out that there is a proper time and a place for sex, and abusing it is unhealthy...

In 1 Corinthians, Paul argues for monogamy, but the attitude of this passage is not one of laying out basic moral law, but rather one of a wise mentor advocating restraint to a specific audience in a specific situation. I could elaborate further, but the long and short of it is that most of what modern christianity teaches about sexual morality is on shaky biblical footing at best; I personally think polyamory is within the bounds of biblical morality.

I realize that most people don't care about biblical morality, but the bible has a lot of good advice, and I think it warrants some consideration even if you don't accept it as axiomatically true (which I do not) as most modern christians do.