I'm sorry but this isn't quite true in some of my games. Bismarck, too, for example, will plot against you despite the buffs, if you have any army smaller than his. Ditto Indonesia. These too are, I'm certain, hard-coded to be obsessed with lebensraum and taking it from the human player.
Overall, your post was quite accurate to my experience, kb, but this one part is not quite on the mark IMO. Sometimes different AIs will be unbribeable.
I agree that the best defence is offence. I'm from the Mearsheimer school of Civ 5. This just doesn't work against Oda cuz sometimes he makes 2-3x more units than Ashur or Attila.
Oh yeah I forgot about Dido (evil!), Germany and Aztecs too... oh yeah and fatty-ass Gaja too...
but plotting against someone (steal tech, prophet bomb holy city, coup CS ally, beat to wonder etc.) and actually DOWing is quite different.
We're not talking about war bribes; Budwiser was talking about something prophylactic: giving them stuff for free in a deal made on your behalf.
Bribes are by far my least recommended solution and a last resort. If you bribe often you will soon find yourself in a difficult position where it is impossible not to make more than one enemy (civs that you put to war with each other often will denounce each other once the war ends... they will force you to take sides... so I'd rather block than bribe); once you have multiple enemies, they will invite each other to war with you even if they are a million hexes away from your borders (see above); once you are in a war the odds of even a friend (esp not so loyal ones) DoWing you is greatly increased.
Anyway, let's say you've managed to befriend them (returning civilians, shared religion, giving gifts for free and whatnot) AFTER you've DOF'd if they ask for stuff for free and you gave it, I'm 90% sure even Germany will not DOW you; the AI is coded to work to the best interest of their empire and suddenly not having that deal going for them is viewed quite negatively;, unless bribed by other AI (happens once per game and some AIs are more prone to accepting than others, depending on army difference and loyalty flavor) OR invited by other AI (you'll know because the DoW will be simultaneous, and chances are at least one or both AIs have reason to hate you)
The latter one is by far more dangerous as you cannot see it coming (they will DoW you even if they are nowhere near your borders and forming a blockade behind a river will not save you in this instance)
As long as you don't have two enemies you can keep the peace going all game as long as you don't let their army reach your borders; even if your borders are touching as long as you are friendly (or they are pretending, depending on deception flavor which is my favorite part about Atilla or Monty, he's pretending to be friendly and so to keep up his ruse, he gives me open borders for a few strategic resources or gpt... then his plan to attack me kinda fails because I block) having open borders with them is quite easy and it's VERY easy to block as long as you have around 8-10 units or so, even the lowly scout or starting warrior or civilians like missionaries or archaelogists is completely fine... try it); the most dangerous thing is having a neighbor hate you; they will not give you open borders and the trick mentioned above no longer works.
This assumes you've survived until Civil Service of course... we are not talking about battering ram rushes which kill you on t35... but chances are you can find a river or patch of rough terrain in no man's land to block. I always send my scouts home to do this job; in the meantime they also help spot for barb camps and other civ's settlers.
So in my games war is a very rare thing. When you have gifts, mutual friends, WC proposals they love, landmark in their borders it is VERY hard to get DoW'd or even have an AI think about DoWing... they will still plot against you but they won't attack (if you see an army coming even from a friend, you bribe or block anyway unless your spy tells you the attack was launched against different civ) so your goal is to simply have no more than one enemy, then there will be no DoW that you cannot foresee.
Now for the rest of you warmongers who are used to getting chain-denounced, ignore all that I just said as this does not apply to you at all