Relax, guys... if the goal is to merely emulate a human brain, we have nothing to worry about that we don't have already. It's possible such a computer would be even stupider than my Android phone.

The problem with Skynet and similar sci-fi scenarios is that there was basically one node that could control all computer-driven devices through a vast network.
That's why I turn my PC off at night, and I'll never give it robotic hands.