I have a bit of experience in this.
Case one: guy in long term marriage to woman who presently IDs as an asexual lesbian. He has permission to have sex outside relationship. We get together once, make out, mutual masturbation... she rescinds permission (reluctant mono as she is). Their marriage survives, sex has improved between them last time I heard.
Case two: Older gentleman who approaches me for a relationship, telling me he's in an open marriage and had just broken up w his gf of 3 yrs. We have 2 or 3 dates and his wife leaves him, divorces him and moves across country w most of their possessions! Do I take responsibility for this? No fucking way. And this guy gets obsessed w the idea of 3ways or group sex then for some reason and doesnt want to date me anymore. Poor Bastard.
Case three: poly couple my age. Man and I have one date after iming for months. We have sex. After we have sex, he tells me he neglected to tell his wife we were gonna have a date! Months of anguish bwtn them ensue, trust is broken, maybe they won't make it. Do I take responsibility for this? No fucking way. It's not my fault their communication sucks. He's afraid of her, is my sense.
Love withers under constraint; its very essence is liberty. It is compatible neither with envy, jealousy or fear. It is there most pure, perfect and unlimited when its votaries live in confidence, equality and unreserve. -- Shelley
There's no lying in polyamory!
I'm a 58 year old woman with 2 partners:
miss pixi, my live-in gf, 36 (together since Jan '09)
Ginger, bf, 61, married, lives nearby (together since Jan '12)