In Utah (it's always Utah) a judge was recently charged with having three wives.
Normally I'd go after the guy for being a Republican hypocrite, but in this case, I won't.
Now that we have stepped into the modern era by making gay marriages in Canada legal, Polygamy strikes me as the next obvious evolution of marriage (along with contractual limits i.e. 'This marriage is effective for ___ years, with the option for renewal given all parties agree to be set for ____", but I digress).
I don't mean to minimize the damage done by the polygamy practiced in Utah where the 'wives' are usually related to one another (ewww!), and where the brides face incredible pressure at far too young an age to be reasonably said to have given adult consent.
Both of those situations strike me is grounds to oppose the kind of polygamy as it is actually practiced in Utah.
Philosophically though, I'm not sure what the panic is over. If three (or more?) adult people (any arrangement of the sexes works for me) want to live, procreate, keep house together and refer to each other as married - I'm not sure I see what the problem is.
Perhaps Rich at the Lost Boys Survey has some thoughts....