Oh, sorry for the double post...I just thought of a great example using stuff we already had in place.
Hypothetical Anders Romance in Dragon Age 2 With This System.
In the game itself, you could become Arcane Defender or Templar Supporter (based on Cheevos, which means the data was tracked). There were certain quests you could complete that would either favour the Mages or Templars. (And I think there were one or two that had neutral endings.)
Anyhow, if you were to romance Anders, he'd obviously prefer you didn't kill the mages. So, for every Mage-related quest you completed, and saved the mages, you'd earn a point in his book. If you sided with the Templars, you'd lose a point. If you sided with the mages enough times to get some sort of connection with him: he sees you as an ally, someone he can trust, someone he can respect, based on your choices, you'd then be able to pursue a romance with him.
After the romance is active, if you suddenly decide to KILL ALL THE MAGES, eventually it becomes a problem, triggers a crisis state in the relationship, and can possibly end it. (If you don't change your mage-slaying ways.)
All of these mechanics are present separately in the game. Tracking decisions, tagging choices that lead to respect, crisis states in a romance, etc. But pulling it together could make something fantastic.