Ethereum rolled back the blockchain last year in the DAO fiasco, so much for it not being altered.

Why do you need 100% faith in something? Does walmart have 100% faith in their system? I really don't know but I am sure it is close to 100% without a blockchain.

You need a middleman in a lot of things. For instance crop insurance was one of the first things ethereum was being pitched for. The problem is that you need an adjust to go out to the farm and appraise how much damage was done. They can then write the farmer a check. No need for any blockchain.