Delegation can help a firm in at least two ways. First, delegation can allow decisions to be made by the people who are most knowledgable in a given area. Instead of having a manager who is not intimately familiar with a process make a decision, it allows those who are familiar with the process decide. Second, delegation can improve the morale in a firm. It can make lower-level employees feel important and values.
Delegation can hurt a firm if done badly. If a manager delegates work to someone who is not capable of doing that work, the company will clearly suffer. The mistake will also tend to hurt the careers of both the person who delegated the job and the person to whom it was delegated.
Delegation, then, can help a company function better if it is done right, but can lead to bad decisions and damaged careers if it is done wrong.