Except that firewalls do not grow to be GB-sized to be useful.
It has been repeatedly said that blockchain does not scale well. I'm interested in seeing how this is going to evolve, because I doubt that many people have phones that hold a multi-GB ledger in the first place.
Sure, the ledger won't be big now, but if hundreds of thousands of people are adding to it every day, it will get there. So I look forward to an article next year telling us what is happening to this scheme.