That last gal messaged me relentlessly. At least. Kind hearted conversation about the sexual desires and other intimate factors between three and more lovers are the same as for monogamous families. Out of nowhere she demands a complete change. My best friend had the same situation. What I would suggest be the first thing to be discussed is what is his motivation for moving towards swinging, what does he expect to get out of it for himself and how it would enrich the relationship you already or prefer ongoing casual fun and does he feel there is anything missing.
Unfortunately the answer I've given also infers similar issues with offline dating as ultimately this has little to do with the internet and more to do with society. As an internet busybody I hope to add my contribution to this awesome topic that has baffled the greatest and the not so great.
Sounds like you and the wife had an exciting time in Vegas. I eventually met a really sweet girl but the work involved was insane. I met the love of my life my second year of college, and was married before I graduated. As guys our mission is to repair, maintain, oil and fuel.