Have you ever read some of those science fiction books where robots rise against humans and it becomes a war between US and them, and of course they have the upper hand because they are much more logical, can think problems through much faster, they feel no pain, they know no fear and are overall better suited for living in a space age.
Well we are now at the beginning of that age apparently, we are now in the age of artificial intelligence everything almost is being turned over to automation and frighteningly AI is even taking over some thought processes. Now what really worries me is the blockchain, apparently it will be a composite thing which will probably hold most of human knowledge at the rate it is developing. Of course it will probably take different routes in the future but I think it is going to a place where it won't need human interference.
I know this is just the ramblings of somebody who doesn't know much about anything but it is definitely a possibility, maybe the blockchain becomes aware of itself and tries to destroy us. Yes, it is probably dumb, but then apart from us being in the era of artificial intelligence we are also in the era of dumb conspiracy theories so I think this one is as good as any other theory out there.