For me, I really don't care for all the legal mumbo jumbo, and find mia's explanation the most persuasive. Namely, that if I open my door finding a complete stranger, who upon showing me an invitation addressed to another, I not only welcome him in, but also encourage he have some Coke with some extra Jack, only to then several months later accuse the stranger for having crashed my party.

PS - These were Citi driven decisions, and it's unclear to me whether or if AA has *any* legal obligations here.