interesting...I just got wiped out in my latest game...king difficulty, playing as Alexander against Napoleon, Cathy, Mao, and Elizabeth. Only Cathy refused to backstab me repeatedly. Each of the others demanded something of me every few turns, and if I said no, declared war on me. I eventually lost in 2100AD with France building the UN and Elizabeth building the World Bank(and I had only one city left, on an island far away)
It didn't help I started smack in the middle of all 4 of them, but I hated how even when my military was bigger then theirs, and I had more culture being produced across my empire, I was close to losing cities to culture, and I was repeatedly thrust into a 3-way war.
Oh...and I did see the AI declare war on each other repeatedly, but France and England never declared war on each other, and none of them ever actually did any damage to anyone but me.