IT, Finance, Accounting, CIA, FBI... I don't think it matters so much which group owns AAIs as long as it has a really good understanding of how AAIs work and it has the communication skills necessary for gaining input from, and giving feedback to, all the affected managers.
In the interest of securing the ongoing proper functionality of AAIs, its a good idea to have a small and tight knit cadre doing the dirty work with the AAI tables BUT I think you want to make sure they are not making any AAI decisions in isolation.