Advantages: Enabling horizontal communication in an organization, encourages free information exchange. Higher information flow between departments is necessary so avoid the same problems being faced by different departments. Hence, information exchange leads to lesser redundancy. Also, horizontal communication makes an atmosphere where employees are comfortable to talk to people in different departments and gain from their learning.
Disadvantage: Sometimes, horizontal communication leads to disputes between individuals/departments. In such cases higher officials have to step in to resolve the matter.