Mt. Gox

A card site becomes a bank

Mt. Gox began as a name for trading game cards and became the dominant early Bitcoin exchange. Users did not merely trade there; they let the company hold the keys. The interface made a decentralized asset feel like an ordinary account. That convenience quietly restored a familiar institution: a custodian whose internal ledger stood between customers and the public chain.

The ledger did not see theft

Coins leaked over a long period through compromised credentials, accounting failures, and transaction-handling weaknesses. On-chain transfers were valid in the narrow sense: properly signed transactions entered blocks. The chain could not determine that a signature came from someone who had no rightful claim to the customer’s balance. Cryptographic authority and legitimate ownership had separated.

Bankruptcy creates another measure

When Mt. Gox collapsed in 2014, missing bitcoin, later-recovered bitcoin, yen claims, and market appreciation became different ledgers. Legal proceedings had to decide who counted as a creditor, how claims were valued, and how recovered assets would be distributed. An immutable history did not eliminate interpretation; it delivered unusually exact evidence into an institution that still had to name the loss.

The lesson is not “not your keys” alone

Self-custody removes one intermediary but transfers security work to the individual. Custody can be useful and even necessary. The deeper lesson is to keep separate four claims often merged by an interface: the chain moved coins, a company controlled keys, customers owned claims, and a legal process repaired what it could. They overlap, but none proves all the others.