It's slightly unclear whether the OP is talking about risk assessment and reducing unknown unknowns, or simply advocating becoming more well-rounded in your problem domain.<p>Also, I would argue there's much more to consider before offhandedly determining anything you don't know "is the riskiest part of your business". The real answer probably lies in the question: Can I hire somebody to do this, or is it important enough to distract us from other goals? If yes then do it, otherwise reconsider when resources free up.