Gangbanged a woman twice. I'd probably try it again with someone else, as this particular girl was into being degraded (spit on, slapped, choked hard, etc.) which I'm not into, but was curious. The other guys being around was a non-factor. It was akin to being in a locker room after a game, but instead of showering, a chick with a phat ass and huge boobs comes in and we f*** her.
As far as actual polyamory, I dig it as it works better for me and what I want, although I haven't completely written off monogamy. I guess you could say I have a few polyamorous 'girlfriends' around the globe, but we don't define things. When we are together we are a couple, and when we aren't we live our own lives. It's quite nice.
They are unhealthy and against nature. We are biologically and evolved to want bonding with one person which is why jealousy among relationships/marriages happen.
I've got no science or stats to back this up, but I disagree. I grew up observing social animals and watching nature docs, and the common thread I've noticed that seems to carry over across different species is that females bond to the males that provide them with access to resources/territory, whether that's one male or a coalition or brothers/allies. This is why we have the "20-80 rule" and why some women will put up with a desirable man cheating/having side pieces. Somewhere inside they know it's the nature of the game. The jealousy I feel like comes from monogamy and the idea that she has to be "the one", thus any other is a threat to her position.
Men I feel like are designed to be, for better or worse, possessive of those females. I think the severity of that possessiveness comes when we have to 'put all of our eggs in one basket' vs. spreading them between multiple baskets. If I've got 4-5 baskets, I won't be to screwed if I lost one, but if I only had one, it's a disaster. This is why I think men generally take rejection and breakups worse than women.
Just my guess.