Have participated in a fair number, early on it was a bunch of horny 19-24 year olds, a few married kids mixed in. Then it was mostly couples, foursomes swapping or couples house parties. The drug use of the 1980s & a change in employment to a high profile job led me to drop it. In recent years I've returned to threesomes and groups.
Never contracted a std in all that, but did from one on one with single ladies. Now I try to be careful with partners & use protection and clean up throughly.
As the post above said, with the right people. I'm not about to get it on with a room full of strangers but if it was people I knew or friends of people I knew, then I could see my way to giving it a whirl.