Since it’s a ledger, the coins can’t be poisoned, but you can poison the addresses (in traceable blockchains like Bitcoin, at least). At the bluntest level, refuse to transact with addresses that have received money from poisoned addresses, transitively. In practice you probably want to apply somewhat more nuanced rules, or the poison is far too likely to spread to the innocent. It could even be weaponised, by a poisoned address deliberately sending small amounts to addresses that it wishes to poison, since you can’t refuse to receive a transaction.
(Incidentally also, there is a minimum unit, at least in all currencies that I know of; Bitcoin, for example, goes to eight decimal places. But yeah, each unit doesn’t have physical identity like bank notes do. Infinite divisibility is bad for efficiency as it means your data types have unbounded memory usage, so you’d need to put together a bunch of rules about how far you actually can divide things, and it’s just not worth it.)
> since you can’t refuse to receive a transaction.
Yeah I think this break your hypothesis.
Every single major account will just end up poisoned. Easily done by finding the addresses with most coins and sending them fractions of coins from tainted account. Tesla will be the first.
It doesn’t break the concept of poisoning, just the naive, trivial implementation of it. Major players in any sort of payment systems will absolutely be doing things like this, just with more complex rules and supporting analysis.
(Incidentally also, there is a minimum unit, at least in all currencies that I know of; Bitcoin, for example, goes to eight decimal places. But yeah, each unit doesn’t have physical identity like bank notes do. Infinite divisibility is bad for efficiency as it means your data types have unbounded memory usage, so you’d need to put together a bunch of rules about how far you actually can divide things, and it’s just not worth it.)