BitcoinTalk user Stone Man accidentally wiped the private key for the address containing 8999 BTC back in 2010.
$167ZWTT8n6s4ya8cGjqNNQjDwDGY31vmHg
This was before modern xPub master seed wallets were used, so for every address used the wallet had to store the associated private key for it. If you were using a temporary live version of Linux running from a CD like this user, that meant backing up your private keys after every transaction. Unfortunately for Stone Man, not understanding this [...]