There’s tons of answers to this, but one example I’m interested in is as a good shared, accessible audit log for data throughout an organization. Just having a stable history for all data helps with investigation and master data management.
In this case consensus isn’t really necessary because all participants are trusted and should rarely differ (since they all have the same boss at some level).
I agree. But working at a huge company I can honestly say they don't really want an immutable ledger. They want to fudge and change things.
Typically a ledger should be immutable. That's what retains its auditability. Any fudging/changing should be done through reverse entries that explain why the reversal occurs.
I suppose maybe it depends on the organization. I’ve worked at companies that do want an immutable ledger. But probably not have it be public.
To tell which document (transaction) of a given pair correlated ones was issued earlier, which is called "timestamping". But you don't need consensus (as in Byzantine generals problem) to do that, you just need timestamping protocol.