I don't think that the exciting part about immutability in large scale distributed systems is immutability itself, but rather referential integrity--particularl

I don't think that the exciting part about immutability in large scale distributed systems is immutability itself, but rather referential integrity--particularly from names to arbitrary data (usually seen as cryptographic hashes that function as pointers). If that reference is mutable then there needs be some authority that handles which names resolve to which data at which times. This makes it difficult to determine at time t if the bits you received at time t-1 were the right ones for some name. In immutable designs the complexity of deciding "which version?" Is moved up in the stack (where the answer is typically mutable). In many cases, pushing this complexity out to the user is indeed the right thing to do. Sure, the ability to resist a government's desire for censorship _might_ be a design goal, but there are other reasons to prefer immutability.