I've been feeling badly over the last few weeks about the demise of Nau, the sustainable sportswear company that seemed to be the very model of transparency and authenticity in their operations and marketing. Being transparent and authentic is something that I always recommend to clients, you see, and now the company that was my primary example has fallen flat.

That's led me to add a new, key recommendation to my advice: make sure you business model is a good one. All the sustainability in the world won't keep you afloat if your business model isn't successful in linking you to customers and ultimately driving sales.

Of course, Nau may have had a perfectly good business model and just ran into hard economic times--something that can happen to even Fortune 500 companies .

I'm hoping that some smart MBA will dissect the Nau failure soon, so we all can draw lessons from what happened. And, I'm hoping that the very model of sustainability that they offered will be picked up by the Naus of the future and taken to yet higher heights.