The smaller the company, the higher chances that there is an employee who has the knowledge whose loss could turn the company to toast. Most likely, that employee is the founder of the business, however in other cases he could work at a lower level. Big companies usually have a detailed process and plan in case such an event comes into play. When Steve Jobs, Apple’s CEO, fell ill, the company had a successor ready to step in, leaving no space for error. Unlike the big guys, small businesses usually don’t look beyond planning for succession, usually as a result of limited resources and time.
The result can vary from a growth slow down to revenue loss to a devastating crisis.