There are several problems the the idea of monogamy as it stands in our culture. Not least of which is the needless suffering its supremacy causes. It is widely believed (assumed?) that monogamy is a precondition of a stable long term romantic relationship. This belief stands on nothing other than tradition and traditions typical allies. To this unsupported ideal we sacrifice many things; all needlessly, passionately and wrongly.
The most obvious and damning complaint about monogamy is that it basically never happens. It doesn't happen in human marriages, it doesn't happen in animals that bond for life, it happens very rarely. And it fails to make pragmatic sense to hold people to a standard that is itself the exception. It would be like calling death before the age of 85 a moral failing and people who didn't make should be shunned. Such a move would add a layer of guilt and recrimination to funerals of people who merely succumbed to their biology.
The second issue with the universal permanent demand for monogamy is how cruel and selfish it is. We all want to sleep around to one extent or another, and done properly and responsibly the occasional dalliance is incredibly enjoyable. And to deny those pleasures to your partner purely out of a combination of ill founded insecurity and unfounded tradition seems to me to be the antithesis of caring about one's partner.
There is more to fidelity than exclusivity. Caring about and staying true to your partner includes caring about their sexual pleasure, which can not be totally satisfied by a single person for the rest of you life (or until the divorce). Both parties in a relationship are going to want to stray from time to time and forming a mutually assured destruction pact about that fact, not only causes a lot of heartache and misplaced blame; but it doesn't even get the mutual exclusivity that we are told that it will. Chances are you're either going to get dumped or cheated on anyway. So why can't we be adults about it and pull the gun away from the head of our relationships? Why can't we discuss what we want and negotiate a new solution to the problems of sex in an overcrowded culture. It can be done, it's not always fun and it's not without its risks, but we must admit that the status quo for monogamous relationships is a dreadful sham.
So on this Valentines Day, think about giving your partner an unusual gift, novelty.