This is where I would have to agree, there are many different consensus mechanism coming to light as time goes by. Most of you are assuming it would be costly because of PoW or similar mechanism in which require transactions fees in a fully decentralized network, that is a foolish assumption.  Now the real questions boils down to scalability and not about it being costly, with many start ups focusing on providing scalable solutions this should one day be out of the question also, so at this point in time the only real question to ask is how fast does it need to settle? is security more important than time? most of the time it is, as the whole process does not need to be decentralized only the end product.

Even so this does not fall under Bitcoin's Development and Technical Discussion. This is not a Bitcoin related question and Blockchain is not solely meant for use in cryptocurrency.

and as far as Blockchain and Machine Learning in relation to AI, it could allow for AI's to just become smarter and smarter overtime without them really being able to be stopped in a far out future. They could have "memory states" on the blockchain in which they would be able to access at any point in time, without anyone having the power or access to really control them centrally, most organizations have their code and are easily able to monitor or stop any activity on sight but now if we where to use blockchain they could just save their "memory states" on the blockchain and access them from anywhere with internet connectivity. If you see I-robot where Will Smith has to go to a central location to stop the bad AI well in such a case it would prevent such thing from being possible. Still something for the far out future where we are in a world where AI just keeps on advancing who knows.