A response to Validation in a DDD world

Jimmy Bogard presented a well written argument for always keeping validation out of entities in a domain driven design except in "the absolute worst case." But, IMO, there is simply no black and white verdict on where validation must live in a DDD application and must be carefully considered at the beginning of any project, taking into consideration the motivations behind validation, the scope of the project, the maturity of the development team, and the balance between philosophical purity and practical maintainability.