Glenn thinks that a lot of the current concern about polygamy is an offshoot of the gay marriage debate. I think that’s right, but we need to clarify terms here:
There’s a pretty good argument that polygamy is usually bad for the societies it appears in, producing a large surplus of sullen, unmarriageable young men.
Polygamy per se (a marriage of more than two individuals) doesn’t result in frustrated young men–that would be polygyny (the specific case in which it is one man married to multiple women). It could be balanced out with polyandry (in which one woman has several husbands). Judging by the fact that males are…ummmmm…orgasm challenged relative to healthy females, and the prevalence of porn fantasies (and perhaps real incidents, though I have no personal experience) about one woman satisfying a number of men, and all enjoying it, at least at the time, could in fact be popular if it weren’t for that pesky male imperative to know whether or not your kids are really yours.
But I’m not aware of many societies that have general polygamy–it seems to be one or the other, with polygyny dominating for fairly obvious evolutionary-psychological reasons.