I started to make this 'friends only' due to LJ names, then decided to remove those (this is about me, not them). I've always said I have nothing to hide, and all of those mentioned are here on LJ and can see this. If anyone named wants to speak up and clarify anything (or ask me to fake their name), feel free.
It was years before I really gave it more than a cursory thought. Mostly, I was not in a position that would have been conducive to it. Once I set my life to be as drama-free as I could keep it, I gave a lot of things more thought, norms of society and what was taken for granted. This started in my late teens, and continued through my 20's. I made a lot of choices about my position in life, society, and the world.
I think I started to really think about it when I cut off ties with my family, because it made me think about who was actually important to me. As my Tribe was formed, I considered the fact that I could openly say I loved each of them, and that led me to realize that love was boundless, and no matter how much I gave anyone, I had more that I could give. At the time, it just made me feel...larger than myself, I guess. Now, in my youth I'd been involved with some odd crowds, so I knew about polyamory, but had not bothered to think deeply about it.
I didn't start to consider it more until I met Heidi, a friend I made online while I was engaged to Mikki. This was nothing more than friendship, but as we got closer, I felt those feelings growing that I knew were love, and it was echoed by her. I felt bad about that until I thought about it and realized I didn't love Mikki any less. Hell, I felt even closer, in a way, because I felt like I had found something that was missing. This was not about sex; Heidi lived a thousand miles away. To this day, there's only twice we've been in the same room. This was an emotional connection, but it was additive, not subtractive. Obviously, it never went anywhere for various reasons, but it was the first time it truly hit me. Eventually, Mikki and I broke things off, though we're friendly even today.
Obviously, there needs to be a lot of communication and openness in a situation like this. It's not for everyone. Just recently, I was talking to my ex, Emily, and the idea of us being back together came up (keep in mind that she still lives in Memphis, so this was kind of academic), and she outright admitted that, in the end, a major obstacle was that she wouldn't want to share, and she'd always either feel like "the other woman" or feel like she was making Di feel that way and neither was something she would want. Fair enough.
As for Di and I, she's not jealous. Jessica had been a friend of mine for years, long before I met Dianna. She and I were incredibly close (3am calls, crying and depressed, etc.) and I was quite open about the fact that I love her deeply. She's very important to me. Once Di and I got together and were serious, she was understandably curious about someone that I was willing to stop whatever I was doing to take care of, and was perfectly fine about it all when I told her. After all, I wasn't cheating on her, hiding anything, this was obviously something serious. As it turned out, I got the two of them talking as well, and things blossomed between them as well, to the point that we had plans to help her move out here to be with us. It was perfect and beautiful, we each loved each other. What happened there is a story in and of itself, and not connected to this, so ask me another time. The fact is, it would have been excellent, and did not fall apart due to the situation.
So, here we are. Di is still openly looking for a girlfriend, and I support it. I am also keeping an eye out for someone that would expand my life, and she supports it. Neither of us is jealous of this, as we both feel the same way about our ability to love. My love for anyone else does not diminish my love for her. As for sex, we both make the distinction between love and sex. Yes, sex can be something that is great with someone you love, and it can also just be a hell of a lot of fun. And, really, that can be said of any activity. If I make dinner for someone I love, I may do it differently, or put a little more effort into the atmosphere, or share it in a closer way, but I still cook for other people, too. We are open and honest about whatever is going on, and fully disclose plans and thoughts. If I was trying to have a date with someone, she'd get out of the house for the night, or whatever, and vice versa.
It's truly all in the communication and the ability to just relax and enjoy life. Drama-free is the way to be. That seems to be the difference I've seen in a poly relationship and an open one. I believe that the connection makes the difference. I'm not saying there's anything inherently bad with an open relationship; a good friend that was in one explained it as the fact that his girl didn't want to emotionally share him, but recognized sex as simply a physical act. Regardless of who he was 'doing', he always came home and loved her, and she was OK with that. Poly goes a step further and understands that love is infinite.
So, wow, this got a lot longer than I expected it to be. Glad I didn't hijack their post with this. ;)