The reasoning of most of the people on this site and at MIRI is that to prevent an AI taking over the world and killing us all; we must first create an AI that will take over the world but act according to the wishes of humanity; a benevolent god, for want of a better term. I think this line of thinking is both unlikely to work and ultimately cruel to the FAI in question, for the reasons this article explains:

http://hplusmagazine.com/2012/01/16/my-hostility-towards-the-concept-of-friendly-ai/