Decentralized Autonomous Organizations (DAOs) are increasingly popular, and already managing many billions of dollars in treasuries. Their decentralized governance is a transformative new way of organizing communities. But as they grow, DAOs will face a new and potent threat to their decentralization - Dark DAOs. A Dark DAO is a private smart contract that targets a legitimate DAO, attacking its voting integrity by enabling vote-buying among its users. First considered in 2018, Dark DAOs haven’t yet appeared in the wild — but only because DAOs are not very decentralized today. As DAOs continue on a path to higher decentralization, Dark DAOs will inevitably surface. Vote-buying may be illegal in political elections, but in DAOs it’s probably legal. It’s legal in shareholder voting and there’s even a marketplace to facilitate it. Vote-buying in DAOs would follow the trend in Web3 of monetizing everything from people’s friends to maximal-extractable value (MEV).