The 'grapevine' refers to the informal communication network within an organization, distinct from official channels. It transmits information rapidly through personal conversations, gossip, and rumors. The characterization of the grapevine as a 'necessary evil' aptly captures its dual nature, highlighting both its indispensable functions and its inherent drawbacks.

Why it is 'Necessary':

1. Speed and Reach: The grapevine often transmits information much faster than formal channels, especially during times of uncertainty or crisis, reaching employees who might otherwise feel left out.
2. Fills Information Gaps: When formal communication is slow, incomplete, or perceived as untrustworthy, the grapevine steps in to provide explanations, even if speculative, helping employees make sense of their environment.
3. Social Cohesion: It serves a vital social function, fostering camaraderie, building relationships, and allowing employees to share concerns and build a sense of community.
4. Feedback Mechanism: Management can sometimes tap into the grapevine to gauge employee morale, identify potential problems, or understand how policies are being perceived at the ground level.
5. Emotional Release: It provides an outlet for employees to express frustrations, anxieties, and opinions, acting as a psychological safety valve.

Why it is 'Evil':

1. Inaccuracy and Rumors: The most significant drawback is its propensity to spread unverified information, rumors, and gossip, which can be damaging to individuals, morale, and organizational reputation.
2. Distortion: Information can be distorted or exaggerated as it passes through multiple individuals, leading to misunderstandings and misinterpretations.
3. Lack of Accountability: Since there's no official source, it's difficult to hold anyone accountable for the information disseminated through the grapevine.
4. Negative Impact on Morale: Harmful rumors or negative gossip can create anxiety, distrust, and a toxic work environment.
5. Undermining Authority: The grapevine can sometimes spread information that contradicts or undermines official directives, challenging management's authority.

In conclusion, the grapevine is an inevitable and inherent part of organizational life; no organization can completely eliminate it. While its informal nature makes it prone to inaccuracies and potential harm, it also serves crucial social and informational functions. Effective management doesn't ignore the grapevine but rather acknowledges its existence, monitors its flow, and proactively counters misinformation with timely, transparent, and accurate formal communication. By understanding and managing it, organizations can mitigate its 'evil' aspects while leveraging its 'necessary' functions.