Well Kasnavada, you may have some points there, but if you make a NAP "in game" and you play a Moloch... that is a Demon, isn't it? Demons do NOT keep their words
. Or if you have a Blood fountain as pretender...
What about a Kraken? Or a Gorgon? Or a dragon? Those a treacherous beings. Also a Prince of Death or a Vampire Queen. If we make a list of pretenders: how many are "lawful" (in the old D&D term) and so should keep their word?
At least from my point of view this hasn't many sense so I forget about those things and follow my wargame mindset. I make a treaty with the player and, unless we have in our mind in a setting like the one llamabeast just proposed where we expect a backstab, I keep my word and expect the other players to do so. OF course, that is the standard setting.