I think I've come up with an application for which #Blockchain is a valid, appropriate and economical solution: reusable containers for perishable liquids (I'm specifically thinking liquid milk but actually it could be anything).
Each container has a built in NFC device with some static RAM. It's initially digitally signed by the manufacturer. Each subsequent fill, clean, etc of the container is recorded with date, time, operator pretended to the chain in clear text and the whole GPG signed.
@simon_brooke sorry, like all provenance systems you need to trust the operators; the end user needs to care (do you currently lack confidence in reusable containers), and you need broad refusal of un-validated items, and full chain of custody otherwise it falls back to trust everyone. E.g. operator A fills with virgin olive oil, B buys and swaps for cheap, then on sells to C, D, E. E thinks they got something they didn't (last blockchain is A).
Even with full chain, if B can still sell in unmarked containers, they can profit, i.e. end consumers need to care enough to refuse, e.g. diamonds (or high value luxury handbags), not recycled containers.
@sgryphon With a full chain you have provenance. With provenance you can sell a premium product. You also have traceability on how many times the container has been used before and, critically, when it was last sterilised and tested.
And the cost of this is absurdly low. It may even be cheaper than current bulking systems.