Umm? Maybe you misread the title: "Off-Chain Transactions" which according to the article: "An off-chain transaction is the movement of value outside of the blo

Umm? Maybe you misread the title: "Off-Chain Transactions" which according to the article: "An off-chain transaction is the movement of value outside of the block chain." So yeah, an exchange like Mt Gox can not prove they own the USD they should own, but can prove they own the bitcoin they claim to own. How is this a problem or limitation of bitcoin again?