Valuable post. Self-revelation is hard! I commend your account in this kind of forum. There are many considerations here, first and foremost of which is that emotional makeup a) differs greatly between people and b) is more set than we care to admit; i.e. not subject to hacking. If Alicorn's is to this degree, more power to her. Before the rest of my comment (as a mono): this is most emphatically NOT a moral judgment about polyamory. Consenting adults, will defend to the death your right, etc.

Other considerations (for someone like me, which maybe you are or are not):

• I'm often on the defensive when polys talk to me, because there is a good bit of evangelism and insistence that monos are morally inferior, emotionally immature, etc. I didn't get that at all from Alicorn's post but it's out there, perhaps as a counteroffensive to monos who do express moral judgment. (Smart polys, police this so we can all have a real discussion!)

• In my personal experience, many of the people who think they're capable of polyamory are not honest with themselves, and once a partner starts seeing someone else, they experience bad jealousy which they're uncomfortable admitting, because after all they're not supposed to; they're poly! Polyamory is going to TEND to favor a) people who become less attached emotionally in relationships; b) people who are very outgoing and popular (i.e. attractive people); c) women at younger ages (mid 20s) and men at later ages (30s onward). Sure, if you're Brad Pitt, be poly! Why not! Think of the population dynamics if everyone was polyamorous. Captains of football teams and cheerleaders as the primaries. The rest of us, gazing adoringly upon them while we wait for our turn on Tuesday night. Then back to the romantic ghetto. That's a bit extreme, but it's a serious thought-experiment about an all-poly-world.

• Marriage is in large part an economic institution focused on child-rearing. Polyamory is a better arrangement for young non child-producing couples than for people who want kids. Are primary poly relationships, even like Alicorn and MBlume, as stable over time as mono? As good for raising kids, if that choice is made? As happy? (I don't think we know. Data?) And the whole idea of wanting someone as the primary means that, given enough time, you WILL meet a more amazing person years down the road, and one of the primaries will lose when you're overcome by the temptation to upgrade. Because of the way human brains relate attractiveness to fertility differently for different genders, this is going to give men an advantage over time as in c. above. One of MBlume's secondaries is going to knock his socks off and 12 years from now Alicorn might get demoted or fired. Or vice versa, but happens less often that way - again, personal experience, and we need data, but it was Alicorn who changed her lifestyle to be with MBlume, so it seems MBlume is the one with the upper hand, and this will increase over time. (Note: this is the main long-term reason I'm not interested in polyamory, at least for even half-serious relationships.)

• Explicit symmetrical polyamory has never emerged stably in history so far. It's worth asking why. Maybe this is coincidence; maybe something has changed now that will be more conducive, but I think it's worth pointing out. For example, a higher prevalence of non-child-producing adults. More questions for actual studies.

• So far I've been discussing polyamory as a hetero practice. I don't know any gay polys but it would certainly be informative to see what's different if anything about gay polys.

• If you can do away with your emotional need for monogamy, why not do away with the need for mates and reproduction completely? I would frankly love to become asexual so I can think about other things for more than 2 minutes at a time! Not in the cards. (If you know a pill I can take or a meditative technique please hook me up. Then I can be nihilamorous.)

• Finally, a lot of polys seem to be doing so partly because they get a buzz from being part of an alternative lifestyle community (affective death spiral, anyone?) While that was a bit of a low blow, I do think it's worth examining this in ourselves, especially with regard to whether choices we're presumably making for the rest of our lives are really sustainable. Kind of like diets, but even more important.