From: Ottawa, Canada
abj9562, the fact of individual victory conditions should be enough to encourage powers who are otherwise allies to consider and even undertake activities that are in their own self-interest (and therefore are the optimal plays for them) but harm one another.
For example, the USSR, in particular, is often known to invade Persia and sometimes even Iraq. This takes 2 objective hexes away from the CW and oil away from both the CW and France. It is generally in the USSR's best interest to do so even though it harms the Allied coalition as a whole (since it also usually takes away 2 US entry chits, delaying American gear-ups & entry into the war by a turn or two), since if done early enough can substantially strengthen the USSR vs. a German invasion. In many games, it is optimal play, from the USSR's perspective if not from its Allies' perspective, to attack Persia & Iraq.
Also, recall that if you liberate an objective hex that originally belonged to your ally, even though you revert control of that hex to your ally you still get credit for the objective. The US, then, has an incentive to beat the CW to the punch in liberating Rabaul, Batavia & Singapore; and in the case of Rabaul & Batavia the US has an incentive to allow the Japanese to capture those objectives instead of passing options that might prevent those occurences.
Also consider the matter of liberating France. From the perspective of the Allied cause as a whole, the best power to do that is the CW, because otherwise France and the CW will not cooperate after France's liberation. However, this would give the French objectives to the CW; and the USSR/French player would not find that optimal. Neither would the US player (who would much rather get the extra objectives himself).
On the Axis side, Italy generally needs German help to do anything substantial, and in general it needs German lending of resources, oil & build points just to last through the game. But the Italians cannot afford to just blindly follow the German lead - if they are to be of any use to the Axis they have to look at expanding their security perimeter and surviving as long as they can. It is always in Italy's best interests to have Gibraltar secured, and the Italians should argue that the Germans make some effort at attacking it, no matter how slight, every game. That is good individual play on Italy's part, but it might be harmful to the Axis cause as a whole if it expends too much of Germany's strength.
I don't know how well the AiA will be able to model that. My own multiplayer experience suggests that human players have no problem simulating the real-war shakiness of the opposing coalitions.