2-sided marketplaces are an extremely powerful force. Entire industries are being disrupted by the power of marketplaces like Airbnb (hospitality), Uber (transportation), Elance (Work), but building a 2-sided marketplace presents incredibly higher risks and challenges than the average product/market fit journey of a startup. In this workshop Sal Matteis covers some of the challenges one faces when building a 2-sided marketplace and provides practical *hacks* on how they can be overcome.