Just watched Sex in ’69: Sexual Revolution in America
(2009), a special on the History Channel (although I believe it was produced by A&E). There was quite a lot of it devoted to open marriages and group sex at the clothing-optional Sandstone retreat. The word "polyamory" wasn't used. They included excerpts from Sandstone
, a documentary by filmmaker Jonathan Dana, who shot it while living there with his then-wife for 15 months. In an interview segment, Dana spoke about his experience living and shooting there, and said that while there he and his wife met another couple with whom they lived in a group marriage for several years after the retreat closed.
Sex in '69
was pretty good, though it really only touched on the topics briefly. However, it wasn't sensationalistic and I quite enjoyed it. If you have the chance, you may want to check it out. Here's a clip, from the distributor's website: http://films.com/PreviewClip.aspx?id=19040