For machines to take over it is required two curious abilities that humans do not master yet: Self replication and self repairing. No device can rule humans if not carrying these skills. No single robot will decide our destiny if it is not self-aware and capable of desire. The only out-of-control-technology threat to mankind might be the grey goo. It is a nanotech hell of tiny machines replicating uncontrollably until they destroy all life on earth. When nuclear weapons were only a project it was suspected that a single detonation was going to spread through the whole universe and bring it all to an end. It did not happen. So even the grey goo is perhaps just too much fear. And same as nuclear bombs no grey goo or tech-doom will prevent people from trying new things.