One of the most misunderstood principles of business deals with the one or few individuals in a small business operation who are critical to operations. This individual is referred to as the Key Man. The best example is that of the primary wage earner in the family unit.
Some individuals are essential to businesses due to their creativity. This is often true in the arts or entertainment industries. Without their input, the business will not be as appealing to the customer/buyer of these skills. Think about how difficult it is for advertisers to provide variety in generating advertising or marketing for clients.