I don't think it is something to be judged right or wrong. The rules of the present society was shaped up on certain aspects of practicality. But if we see in the nature very few species are monogamy pairs.
Even our closest ancestral great apes have this. Now having said what is natural, lets look at the logic why society imposed monogamy rules on people. Mankind is one of those few species on earth that spends long juvenile life. The cost of parenting is high, so as to limit the chaos from littering around. And producing untenable number of offspring human civilisations imposed such rules like monogamy.

Now that having reached the stage where birth controls at their height I wonder does the same principles apply? However, we have developed strong possessiveness in relationships, it is going to be very hard to break out of it. I mean, most of the cultures have helped us build our own shell over the ages, though there are still a lot of chicks walking around free ;)