When a civ completes Armageddon, all other civs declare war on that civ. If that civ also has a bunch of defensive pacts, every one declares war on every one else for declaring war on that civ. My current game just crashed because almost everyone was at war with everyone else on a huge map and my PC couldn't take it.

I was going for a cultural victory too, and the town where he was working on Armageddon had 154 turns left with my Saboteur waiting to stop it, he must have rushed it...must have cost him 10,000 gold...oh well, now I've gotta kick arse on a huge map, meaning this game will last into next week.
When you complete Armageddon, all defensive pacts should first be cancelled before the war declarations.
I possibly recall this being mentioned a few dozen pages ago, but I'm not sure, so I'm repeating it here again in case it wasn't.
Also, I had researched blood of the Pheonix, but none of my nuked units came back to life. That should change...maybe make so that it doesn't work if you are also the civ that does Armageddon to balance it.