Decentralizing the Last Mile in Bitcoin

> an “attack” as any attempt to compromise the central function of a public ledger, which is the immutable public record of settled transactions. It makes no difference how wealthy, well-connected, or powerful a disputant may be — once the exchange is recorded on the blockchain’s public ledger, it is permanent.

This is untrue for Ethereum since they proved they will mutate their chain for specific wallets/contracts (See the DAO scandal)