There's an episode of Star Trek TNG where Wesley Crusher is playing with some nanobots and he accidentally sets them free (or fails to turn them off?), and they go on to replicate, evolve and develop an emergent intelligence (at plot speed). Fortunately for the intrepid crew of the Enterprise, the nanocloud are benevolent enough to forgive their attempted destruction at the hands of a mission bent scientist and go off to explore the universe.

Anyway, that's not likely any time soon, but advancing technology advances the scale of mistakes that an individual can make without asking the rest of humanity what they think.