Not quite the same, but a year or two ago, I was invited to a few "lifestyle" parties. I was amazed at the amount of BB stuff going on. This was a group that met regularly and they implied that it was "closed" to outsiders... apparently, they missed the fact that I was an outsider!
I wouldn't say that "most" sex was unprotected, but certainly a large percentage was. I only went to 3 or 4 events, before I lost interest, but this cavalier attitude was a big part if it. That, plus everyone there was my age and having sex with someone my age is gross. ;-)