Those machines were broken or defective. They didn't go wild. Besides, they all had safety mechanisms the operator failed to utilize such as neutral gear and brakes.
And you've just touched the great unknown, a concept of a thinking machine. A machine that would want to improve itself and become conscious. Such machine wouldn't live by the rules, it would write its own programs. Think Skynet or that thing from the Matrix, a machine that is selfish and doesn't care about peoples lives, it just takes what it needs and uses as it pleases. It wants to conduct experiments to learn and it will use you as a subject, a slave, an organ donor, a living hard drive, you name it.
Before you say it's science fiction and will never happen, think about the needs of such a machine. If it becomes conscious it will want to be everywhere and comprehend everything. It will do anything to learn and won't care about ethics or morality.
This just sent chills to my spine. Uncontrollable machines are really scary to have, especially when they gain consciousness. If it became sentient, it doesn't care whether there is a thing called ethics, moralities, and most importantly, emotions. It will do whatever it wants to do.