I think that what is overlooked is the thought of who is paying for the maintenance of the blockchain ? As time passes that maint. cost increases. The only way to pay what would be the equivalent to miners in any blockchain is if the chain generates income in some way. The cost of that maint. has to be less then a non-distributed system. In many scenarios its obviously much less, in many others it is not. I dont think the blockchain works well with real estate transactions, for example. i.e. I WANT somebody down at town hall signing off on a property transfer even if it is inefficient. Sometimes trust in a non-distributed system is there for a reason.