[LogicalBorg]

The way I see it, there are at least four criteria for using a blockchain.

1. The goods are permanent, otherwise you don't need the history of the blockchain.

2. The goods are valuable, otherwise they aren't worth tracking.

3. The goods are identifiable, otherwise you can't tell that the good you received was the one on the blockchain.

4. The goods came from a trusted third party, otherwise they can receive non-compliant goods and pass them off as their own.

Tracking food on the blockchain fails at all four criteria.

Cryptocurrency passes all four tests. It is permanent, valuable, identifiable, and the third party producer of the coin is trusted because they pass a mathematical test.

Diamonds might also pass the tests, as long as there are trusted third parties in the diamond industry who won't receive bad diamonds.

[hoare]

One of the biggest advantages of a blockchain is it's ability to trust the entries written on a distributed ledger and actions that are automatcally executed when certain criteria is met regarding those entries(This statement ignores the fact that it's still possible to take over a blockchain if you control enough of it) There are a lot of industry specific business cases where the elimination of a 3rd party trust authority would save a lot of money. Remember that not only physical goods can be stored on a blockchain. Consider a contract where multiple participants are required to execute actions in a pre defined order. In theory there are a gazillion use cases for a data structure with that kind of behaviour. In reality it most of the time comes down to the scaling ability of transactions executed/s, which is horrible at the moment.

[Zigurd]

The case of eliminating 3rd parties in transactions brings to mind a further qualifier for blockchain use cases: The application has to tolerate irrevocable transactions.

[Zigurd]

While "permanent" covers one aspect of this requirement, I would add that "You can't or shouldn't trust a database to an otherwise trusted authority."