Imagine I had a Blockchain with all of a nation's citizens' medical records recorded in it.
First: This is a TERRIBLE idea!
Is there not a method to restrict access to each user's records to those who have permission to access them and their own records only?
The basics of access restrictions includes not giving access to people who shouldn't have access. You could use PGP to encrypt all the data, but it's still a terrible idea.
How is a person's computer meant to have enough memory to store all of a country's citizens' medical records if the data is saved on each node in a blockchain?
How is my car meant to have enough power to fly to the moon?