>Who cares what's running everything so long as things get done and the people are prospering?

That's the big "if" - would such an AI put human interests high on its priority list, or will it decide that we're (ie, humanity) more trouble than it's worth and need to kept limited (or even, severely reduced). Would it decide that our concepts of rights, freedoms, opportunities are now quaint anachronisms, and coerce us to a zoo-like existence? And all that speculation is not taking into account that it may feel that humanity has not proven itself capable of self-regulation, and may decide to impose "corrective" measures to restore balance.

There are also possibilities that the human contributors to the AI development deliberately fed it "curated" examples of human behaviour which then skews the AI response to favour certain groups over others.