Can anybody here give a reference to commercial AAA games that implement a machine learning AI?
The most common approach is to train the AI off-line or pre-release, and to ship that final result. As such the game arguably doesn't contain a machine-learning AI.
This is because machine learning can traditionally take many hours of training to produce a usable result, and as it's by definition emergent, it's probably a good idea to put any result through a full QA pass to make sure there aren't any exploitable edge cases.
For the above reasons, and because gameplay changes and balancing even late on might mean that the AI has to be retrained and retested, not many studios use this approach.
Forza's Drivatars are an example of learning AI in a shipped game. They watch your driving to learn how to copy your style. There's lots of information in that link.
The only game I knew that I think may use machine-learning is Tekken 5: Dark Resurrection for psp. in that dojo mode game AI could learn how you play with each one of characters and it created a ghost of you playing that specific character. later you could fight with yourself or give your shadow to your friend and let him to fight against your shadow.
It's not a AAA title, but more of a research game, you create a squad and then train it by manipulating the enviourment, the ai is based on neural net's and the learning is done through GA. NERO
Galactic Civilizations 3 will use a networked approach to AI Machine Learning. Player tactics and strategy will be uploaded to the company servers for analysis. From the Gal3 website faq (http://www.galciv3.com/game/faq):
"Q: : Will the game require a network connection to play?
A: No. However, some of the AI learning mechanisms will require access to the Metaverse in order to perform analysis on player strategies. This will be optional and able to be disabled by the player but does require an Internet connection."
No details on if this is real time, delayed or used in game updates, but the GalCiv games have always been noted (in reviews) for the solid AI.