Frankly I wouldn't want to marry someone who would be willing to share me with someone else, marriage-wise.
Me neither, but I can think of quite a few women who would be more than happy to do this under particular circumstances, and they're not all oppressed women.
Don't women in the West marry old billionaires like Donald Trump or Murdoch? Obviously, the relationship has little to do with love, and all about a selfish deal of wealth for the woman and sex for the man. Methinks many Western women would give their right hand to be Bill Gates second wife or even fifth wife, if only polygamy was legal and acceptable, and some poor pennyless men would be left without wives!;D
George Bernard Shaw said, "Polygamy when tried under modern democratic conditions, like by the Mormons is ruined by the revolt of the mass of inferior men who are reduced to celibacy by it, for the maternal instict leads a woman to prefer a tenth share of a first rate man to exclusive possession of a third."
On a serious note, a society which gives all kinds of freedom to people, from casual sex, to gay marriage, can't just penalise polygamy. But to make it gender equal, first polyandry should be legalized as well & there should be some sort of pre nuptial agreement that the husband or wife won't object to a second spouse.Women from communities where they're not allowed to make free choices should be educated not to be coerced into polygamous marriages, or be forced consent to their husbands marrying a second time.