I normally pick one nation to befriend and offer them only, a DP. If this "freind" turns out to be untrustworthy, I reroll. Usually I pick China, since she doesn't make freinds lightly, ie. if she secretly harbours any kind of dislike for you, you'll never get a DoF in the first place. She also seems low on the "victory competitiveness" thing, ie. if you're close to a victory condition, she won't get jealous and turn on you, unlike most of the others. Of course their personalities all get randomised a little at the start of every game and sometimes she's just reckless, occasionally she hates you too and has a DoW on you by turn 20. At least you can see when this has happened pretty early on and know what to expect.
Anyway, with regard to these DPs... I'm wondering if they are actually worth it.
I was assuming
1) It gives me a Diplomatic + with the Civ I'm in the pact with. Usually i have to throw this out before i can get Freindship with Wu.
2) Coming to the aid of my alliance partner is less of a Diplo hit than just manually declaring War on the agresssor.
3) That is discourages attack on the pair with the DP.
Well, it appears from this thread , that 2) and 3) are definitely not the case. 1) may still be true, to a minor extent.
My latest game, on Prince, started peacefully enough. Well, Caesar had attacked four times by turn 150, but no other wars, no cities changing hands. Anyway, Wu turns up in some cockleshell boat and we're both jostling for attention. She makes a DoF with him first (why dammit, is he just more handsome or something?), but i manage to land a DP.
Then he attacks me again! I immediately get the message that China has declared war on Rome, which can't be good for her relations. Sure enough, denunciations of China follow. But on the "Global Politics" screen, it indicates that Rome "BACKSTABBED CHINA" in big red capital letters. Soon, everyone on my continent has declared War on Rome.
I tried to keep my nose clean by not moving any of my troops into his cities. But I'd had enough of the guy, so i helped Al-Rashid, Ghengis and Bismark capture his cities by eliminating the defences, let them take the diplo hit for taking the Capitol, Razing, and wiping him out.
I kept renewing our DP. The problem is that it's now turned into Me & China vs the World. We're in a permanent state of war. I manage to broker a peace deal with one of the powers for a few turns, then it all starts up again. Everyone hates China and keeps DoWing them, so i end up at war with those guys. And everyone sees me as weak, because i am already at war with so many powers, so i get mobbed by the guys on my own continent. This puts china at war with even more powers... and so it goes on. Strangely, nobody thinks i'm a warmonger though.
I don't know if i can save this situation. It's certainly going to be a lot of work. I guess i need to cripple all the other powers before they get nukes. Given how hard it is to cap a city in this game, that won't be easy.
Ghengis Khan has the whole of Africa and access to plutonium. I'm in western Russia so I should make it a priority to take his north african city with the nuke mine.
Al-Rashid has one of Rome's old cities. I could liberate that and maybe get a loyal ally (though my previous experience of resurrecting Civs is that if they usually continue to hate you if that's what they did in a previous life) and see if that scares the Arabs into making peace with me and China. If not, cripple some more.
The biggest runaway is Askia. He has Southern and Central America all to himself , and 4

. China is in north america but struggling to hold on to Texas in the face of his onslaught. Nothing I can do about this for now, just have to hope China holds.
I guess i made it harder for myself by not wiping out civs i was at war with once i gained the upper hand. I'm haunted by an experience in an earlier game though, where Russia was my ally, and turned on me late game. As well as coveting my land and wonders, Catherine had suddenly decided i was a warmonger. I'm wonder if China will too, when the gloves come off (ie. I start razing, annexing and nuking our enemies?)
Or was that just Catherine being her usual

self?