An AGI has absolutely no requirement to be anywhere near our sort of mind. It has no default obligation to morality that we would find acceptable or safe.
I think the issue here is that when we hear words like "control" or "serving humans" we imagine the AI as a little person in a machine. We associate the word "slave" with the intelligence and imagine an emotional, resentful person whose resentment and chafing at his chains comes from a specific set of environmental and evolutionary influences.
EDIT: I recommend reading Yudkowsky's article "Value is Fragile" (http://lesswrong.com/lw/y3/value_is_fragile/):
>If you loose the grip of human morals and metamorals - the result is not mysterious and alien and beautiful by the standards of human value. It is moral noise, a universe tiled with paperclips. To change away from human morals in the direction of improvement rather than entropy, requires a criterion of improvement; and that criterion would be physically represented in our brains, and our brains alone.
>Relax the grip of human value upon the universe, and it will end up seriously valueless. Not, strange and alien and wonderful, shocking and terrifying and beautiful beyond all human imagination. Just, tiled with paperclips.