[saba2008]

>simply a policy in some implementations

Reversals would mean that there is some authority that can declare arbitrary transaction to be valid or not, and cryptocurrency is exercise in creation of payment system without such trusted party.

So no, would not call it simply a policy.

[_Nat_]

It's definitely a policy, in that it's a design-decision that could be changed to make it operate differently. For example, if a good majority of a crypto-currency's miners elected to fork to a new policy, then it'd just happen.

And cryptocurrency isn't really about lacking a trusted-party so much as decentralizing the trusted-party. Which might sound pedantic, but it's an important distinction: there can be an authority that makes decisions, just it'd be decentralized.

Future crypto-systems, e.g. probably a next generation that'll replace early systems like Bitcoin, would probably take a smart-contract approach. For example, a payment could be reversed under conditions encoded in a smart-contract.

A well-developed system would likely end up including a system of checks-and-balances, appeals, manners of collecting evidence, etc., where trust is decentralized.

For example, most folks would generally agree that a mature, well-developed system should allow someone to recover funds extracted from them under threat-of-violence if everyone agrees that that's what happened. That current systems are too limited to make such an obviously-desirable thing happen is an obvious non-ideality. Once someone makes a good system that fixes such problems, in a generally agreeable way that people can trust, it'll likely become a preferred system; it and its clones, etc., would displace older systems, and this whole no-reversible-transactions thing would become a minor footnote in early history.

[saba2008]

>isn't really about lacking a trusted-party

It's also about minimizing amount of trust to that party. Only thing bitcoin miners are trusted, is determination of correct chronological order of transactions.

>smart-contract approach

Yes, and smart contract will just determine whenever transaction was made under threat of violence!

>end up including a system of checks-and-balances, appeals, manners of collecting evidence

So regular banking, under other name.

Also 'collecting evidence' is pretty much incompatible with anonymity, which is cryptocurrency distinguishing feature.

>trust is decentralized

How is that even supposed to work? Do you expect that every chargeback will be investigated by every mining pool? Or they will have some authority to do it (again, no difference with regular banking)

>most folks

Most folks are ok with current banking system. Cryptocurrency is a niche product, having completely different trade-offs.