In this talk, we will introduce blockchain technologies, describe what it is good at, what it is not good at, and what types of industry disruption it might cause. We will then illustrate how it might be used in three use cases related to finance: (1) decentralized order books, (2) financial audits without a trusted auditor, and (3) decentralized lending for issuing bonds and settling default swaps. These use cases will highlight the potential of blockchains but also expose several gaps it does not cover. The intention is to leave you with a realistic picture of how disruptive it will be.