I have used polyamory rather than polygamy as the -gamy suffix usually refers to marriage, and as yet it is not legal to marry more than one person at the same time (though should it become legal, i would be all for it). 

http://www.anthropologyinpractice.com/2011/06/to-be-or-not-to-be-monogamous.html

An interesting blog posting about the reality and consequences of monogamy in humans, also referencing the low percentage of other primates that engage in monogamy, also raises the issue about perceptions of polyamory (or rather non-married individuals) in general society (I have not read the original article so am not sure of the demographics of the sample set).
 
I was involved in a long term monogamous marriage and since its dissolution several years ago have found out that I am far happier in consensual, open and honest polyamory. My partners are made fully aware of the others, and meet them (the first time this happened was rather peculiar for me, but both men really liked one another). My relationships tend to be long term and committed, while at the same time allowing us to all have a significant level of freedom in our lives.

Hindsight is a wonderful thing. I am no longer the person I was at the time I was married. And as such, I can no longer understand the jealousy and fear i had at that time (occasional as it was) neither can I understand the perception I had that monogamy was the only moral partner status. Of course, at the time I was deeply religious, and that played a significant part in wanting to get married and end the living in sin perception. It also was a status symbol, one that I am now strangely reluctant to admit to. I was also completely sold on the 'til death do us part" aspect and envisioned our entire lives together, something i am sure other people do as well. I am sure very few people start out married life thinking anything but sharing their entire lives together. 

But we, each of us, changed as we matured and for us, we grew apart. in the end, the concept that a single person can be everything and meet every need that we have as individuals is rather preposterous. We do not expect this in healthy friendships, or family relationships. Simply because I have 1 sibling does not make me love the other 4 any less, they simply fill different aspects of my life. I am really lucky to have several close friends and feel that each of them fills different needs I may have at different times. One female friend I love to go shopping with and discuss the intricacies of individual dynamics, another i can talk science to, another will be my best friend throughout life because our personalities match (science talk is banned in her presence) etc. So why do we change this for sexual relationships?

I personally feel there are several factors involved. For some people they really do meet a person who fits them like a glove and do not need to seek intimate relationships with others, but I think these people must be very well matched and are probably few and far between. For others, there is a societal indoctrination that we have learned to accept and thus it becomes the only way for us (this was definitely how i approached relationships for most of my life). And there is personal choice. Some individuals are perfectly happy with one partner at any one time. I have discovered that I am not one of those individuals and to get my needs (physical, emotional, general everyday partnerships etc) met I seek it with several partners while being open and honest with them. Also, what counts as polyamory? Is it full sex with several people, oral sex, intimate touching, kissing, emotional relationships, romantic love, swinging? Where is the line drawn? It varies depending on the people involved, some will engage inall of the above, other only some, keeping what they consider the more intimate aspects of their relationship monogamous. There are no black and white answers.

Another issue is the emotions involved. Do emotions get tangled in polyamorous relationships? Indeed, as they do with any relationship, sexual or otherwise. I still admit to the occassional twinge of emotion at favoritism shown between certain family relationships, let alone friends and my partners.The best cure for that type of thing is communication and not blaming anyone else for your own emotions.

No one can say what is exactly right for any other individual and different things work for different people. I am currently very happy in my situation and know that both myself and my partners have made ethical choices for us. I may one day decide to change or meet someone that I want to be monogamous with. The thing is, I have the freedom to decide and it is, ultimately, my choice.