I have spent a good chunk of time the last couple days visiting The Artist in the hospital. Things are pretty rough for her right now and she needs extra moral support in a big way. On the way home her husband The Steward and I were talking about who we end up leaning on when things in our life go badly. There are some people in everyone's life who make things fun and who are entertaining to be around but when the shit hits the fan they fade away quietly. Then there are others who step up and shoulder some of the burden. The Steward thought that being polyamorous was a real help in that situation because there are likely to be more people with a lot invested in the person who is struggling. His theory is that lovers are more likely than friends to show up and help when the worst happens.
I am not convinced. In this particular case I think it holds because my relationship with The Artist only exists due to both of us being poly - I doubt I would have met her otherwise, much less be as close to her as I am. In general though I think polyamory actually makes it easier for some people to ditch with a moment's notice when things go badly. There is definitely a plausible deniability element to this because cutting off friendships just when a friend needs help is an obviously crappy thing to do but ending a romantic relationship abruptly is far more defensible. You can't be too hard on someone who wants out of a relationship and needs space afterwards and unfortunately that offers a shield to the fair weather lovers.
When things go badly the main thing that poly relationships do is make things more extreme. The people who will rush in to help will help more because the are more emotionally invested. Those who would run away anyhow will run faster and further. That doesn't necessarily mean that the reliable folks are better people to be friends with in the good times but living a polyamorous lifestyle will make it crystal clear who you can really rely on when disaster strikes. I don't really feel like that is particularly an advantage or disadvantage but it is definitely different.
A lot of people talk about polyamory in general as if it is a high risk, high reward prospect. That is, a new lover and the accompanying wonderful feelings and exciting sex are pretty great but everyone worries that there in an inevitable reckoning where jealousy, bitterness, and resentment will come home to roost. I can almost hear the whispered admonitions "Yes, sure, sexing up somebody new sounds great and all, but what about the *consequences*?"
For some people it may be that way but it sure isn't for me. In my life polyamory shrinks that all or nothing feeling rather than amplifying it. If I go through a breakup that makes me sad I can still get my snuggles with someone I love. When I need extra energy or attention from someone there is likely someone who can give it and when I have energy to spare likely somebody needs it. In most of my life having multiple romantic partners smooths things out and moderates the extreme peaks and valleys.
In any case when life delivers a sucker punch it pays to know who will say "I wish I could help" and who will say "I will be there in 15 minutes". Regardless of whether they are family, friends, or lovers those in the second group are the ones that keep the world from falling to pieces.