How many times have you been happily playing along in a game of Civ, and you get 'surprise' attacked by the AI?
Now I know you can keep an eye on the AI by using the demo screens and graphs, and monitoring their attitude towards you via the foreign advisor, but I think the atmosphere of the game would be greatly increased if they contacted you on a more regular basis with regards to their concerns/or lack of. This is the type of thing that goes on in diplo games in great detail, and would greatly increase the flavour of the single player/AI experience.
Case in point. I'm in a game and everything has been peaceful in my neck of the woods from 520AD until 1300AD. I have three neighbours, two direct neighbours and a third very close by. One of my neighbours has been slowly increasing their power until it far exceeds all other civs in the world. They are cautious towards me, and towards our joint neighbour, and also to two other civs, while being pleased with the remaining four civs.
Their current attitude towards me is +3 (+1 years of peace, +2 open borders, +2 mutual struggles, -1 close borders, -1 war on their friend). Most, is not all, diplomatic correspondence in the game has been initiated by me, and I think it would be safe to assume that if anything was bothering them that they would call and air their concerns. Not much I can do about my ancient war their buddy, what's done is done, I suppose a token gesture to smooth over those old sore points. If they had come expressing concern over close borders there could be a mechanism for lessening troop concentrations to reduce border tensions. Other than that, according to their attitude score they seem to be happy(ish) neighbours.
So why on the next turn do they unleash a stock of doom across our border, hell bent on genocide and destruction? It just doesn't seem logical, plausible or realistic. If they had come knocking numerous times asking for me to lessen the number of troops around our borders, fair enough. If they'd asked for help and been refused repeatedly, again I would be able to sense a growing unrest; but these bolts out of the blue just don't seem to fit the grand scheme of things according to our ongoing relationship.
What would be nice to see in CivV is more focus on AI interaction - diplomacy, trade, relations etc. The ability to trade border squares would also add an interesting dynamic as potential hot spots could be exchanged for other land, or cash, units or whatever. In the case in point game, our borders do not encroach on their cities fat X's, but if they did I could have released control of said squares in exchange for something in return, or even gifted them for a further diplo bonus.
How many others would like to see a more proactive AI, coming to you with their concerns, or even to further cemment their friendly relations with kind words and positive feedback.