You might have heard that Blockchain is immutable, but that is a lie!... well not quite, but the ledger is technically modifiable.
One of the many things I found very interesting about the concept of Blockchain introduced by Bitcoin, is how the Proof of Work model works, and how it makes the blockchain immutable (among other things). Specially when you consider that digital data can always be modified, no matter what. The blockchain technology deals with it, and thinks ahead. That’s an important aspect when you are trying to build a system for transferring value in a trustless* way.