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One advantage to vertical communication is that the employee always knows what the boss expects of him.
Vertical communication usually goes from the top down, giving the advantage that Ms. Sue mentions. However, it depends on whether the communication includes both positive and negative comments. Subordinates need positive comments when they are deserved. With children, parents are urged to "catch them being good." In other words, praise them for their positive actions. The same applies to adults. Unfortunately, often superiors only communicate when something goes wrong.
Vertical communication from the bottom up is riskier, because of the power imbalance. Subordinates are taking risks in criticizing actions of their superiors to the superiors, so these criticisms usually remain at the subordinate's level rather than being communicated upward. Suggestion boxes allow upward criticisms to be made anonymously, reducing the fear of negative sanctions for the communication.
However, if subordinates believe changes need to be made by superiors, these changes will never be made unless their need is communicated upward. It is very rewarding for the subordinate, if the suggested change is implemented.
It helps if the superior has a policy encouraging upward communication of both positive and negative remarks. Of course, these remarks are more effective, if they are more specific, giving details of reasons for change and options in making the change. Just saying that something is wrong is ineffective.
I hope this helps a little more. Thanks for asking.