I think Orgies and Group sex is about as old as time. There is nothing new about the idea and it has been accepted and outlawed over and over again through history.
The ancient Greeks were very famous for orgy like sexual behavior. Kings during the dark ages regularly involved themselves with multiple partners and group sex. The French during the 1700-1800's were known for this and even the french word Menaj-a-trois was brought into being.

I personally feel there is nothing wrong with this practice if done in a non-jealousy type mentality. I think it can be a healthy mindset as well, putting into perspective what relationship means and stands for in contrast to an orgy.

As far as something desired on porn, this seems to be one of the top searched for porn content types. So acceptance seems almost universal in secret. There is definitely many people who don't feel they can come out about being ok with or attracted to this type of sexual encounter.

To answer this post, I consider it necessary to understand what Sex Orgy, Sex Party and Group Sex are. All 3 phenomena are united by the idea when more than 2 people have sex at a time, but there is a significant difference between these concepts.
To deal with each of them, I will create separate threads for each of these concepts, where everyone can express their opinion, give arguments and facts.