When you're a single woman on the internet, you get a lot of attention from dudes, whether you want it or not. A fair percentage of that attention will be from married dudes. Lonely married dudes, married dudes who haven't had sex with their wives for years, married dudes who just want to talk to pretty strangers. Over the years I interacted with more of them than I probably should have. I got crushes on some of them. I made friends with others.
Then there are the married dudes in open relationships. I started coming across poly dudes on OKCupid. I seemed to always match highly with them, and much about a poly lifestyle appealed to me, particularly the need for lots of open, honest communication. The thing about being a single woman dating a married man is that she is always vulnerable in a different way than if there are only two people involved. I lost one boyfriend a few years ago because his wife decided she didn't want them to be open any longer. I say "I lost" but what happened is I got dropped like a hot potato. It sucked.
Then there are guys who think your being non-monogamous means that you just want to have sex with lots of different people and have no feelings invested in anything and they treat you like a living toy. And don't get me started on the ones who say they are in open relationships, but their wives have other ideas about that. You must tread very cautiously.
But then maybe one day you get lucky...