The "lean start-up" model has inspired considerable passion in technology entrepreneurship, especially software entrepreneurs. Recent writings and presentations by Steve Blank, Eric Ries and others make a powerful case for an implicit theory of entrepreneurship whose key principles are applicable for any entrepreneur. The lean model posits that a start-up is simply the vehicle for figuring out a sustainable, repeatable, scalable business model: test each critical assumption in your business model; "pivot" (learn and adapt) quickly; iterate. However, the lean? model and its potential often remains misunderstood. (For example, "lean" is often interpreted as cheap, when it is really about being nimble.) We will show how the key principles of the lean start-up model can be used effectively in accelerating not just the scalability of a new venture but also its sustainability.