There's also the magnitude of a negative interaction as well to consider.

If I have 99 great interactions with someone, but one REALLY bad interaction (they insult me deeply, or say something irredeemable), that can also sour the whole relationship.

It would be interesting to research commonalities amongst bad interactions -- are there patterns that emerge from certain personality types, politics, etc? What about a few "sour" people that will take any interaction and make it bad regardless of matchup -- if we removed them from the interaction pool, do the stats suddenly adjust quickly?

In my mind this would have big implications for social media sites -- not that all bad interactions need to be quelled, but if you are trying to keep conversations civil, attempt to implement X strategy or Y strategy.