Monogamy (or more accurately, non-monogamy) has become a hot-button issue in the last couple of years. While various forms of non-monogamy have been around for millennia in non-Western cultures, mainstream Western culture has historically only sanctioned relationships that are sexually and socially monogamous. Non-monogamous relationships have been (and still are) considered taboo, even resulting in legal penalties, despite the fact that a large proportion of people who are in apparently monogamous relationships are not actually sexually monogamous.
The publication of the book Sex at Dawn a couple of years blew the top off this issue. I posted an interview with one of the authours, Dr. Christopher Ryan, earlier this year (link here). Based on a review of all the available evidence, he and his co-authour claim that monogamy is not a natural human inclination or behaviour. Since the publication of Sex at Dawn, many articles have come out questioning the feasibility of monogamy for many people, including the piece a few posts down from The New York Times.
Recently, The Slate published a bunch of great articles on monogamy. If this is an issue that interests you, the articles are recommended reading. You can find them here.