This was really great, I'm pattern matching this idea to the "Win/Win or no deal" mindset from 7 habits. It seems to be the same mindset here , either you both get what you want, or you end the relationship/

Thinking about it, I think one of the biggest reasons that ultimatums may make other people angry is you're forcing the other person to make a difficult decision. For instance, you may know that there is no "win/win" option (eg, imagine that your KNEW your partner wouldn't be happy with polyamory) but you still pose the question so that it puts the other person in the awkward position of having to either choose an option they don't actually want due to emotional dependecy, or be the one that ends the relationship. Sometimes ultimatums are "copouts" so that the other person has to make a difficult decision instead ot the ultimatum maker.

As a side note, does anyone no how to model this type of "my decision is based on your decision" game in a payoff matrix? I tried to do a simple one for the first example (because I'm learning game theory and this seemed like a good place to practice(, but there was not a nash equilibrim where I thought there would be

I ended up starting with this payoff matrix: http://prntscr.com/8lopa4 , then removing the logically impossible options, like this: http://prntscr.com/8loq2b

But that seems to be a really ugly way to do it. and it leaves neither an equilibrium nor even a globally optimal strategy. Is there a prettier way to do it that doesn't resort to two seperate tables like the preference vector example?