What if the world blockchain gets hacked? With such a high stakes reward, there will surely be groups of people interested in hacking it to their advantage.
There will be some people keeping it secure too. Thats also a valid reason why one blockchain to run the world economy is not a healthy choice. Mining if you say so has been the a source of speculation as to what would happen if they got hacked. But they are mostly coming from the weak minds who bought bitcoin hoping it would grow huge but seem to break their expectations. This thing needs to be corrected by only investing what you are willing to lose and not panicking when prices go down.
Again Abiky's thoughts do not match with mine since I believe this is too much longshot. Even though blockchain and AI are buzzwords, it does not mean they are going to be taking over the world.