This is credited to Bill Joy, the co-founder of Sun Microsystems.
The law states "no matter who you are, most of the smartest people work for someone else".
It stemmed from a management dispute over where knowledge is coming from. Joy was basically saying that knowledge is not evenly distributed and if a company is relying upon the knowledge of those employed by it, things will not end well. Solving customers' needs requires tapping into the intelligence outside the corporation.