The level of confidentiality of the information is the most important factor to consider when deciding whether to encrypt it or not when transmitting it over public networks. Confidentiality is the property of preventing unauthorized disclosure of information, and encryption is a technique of transforming information into an unreadable format that can only be decrypted by authorized parties2. Public networks, such as the internet, are inherently insecure and vulnerable to interception, eavesdropping, or modification of the transmitted data.
Therefore, encryption is necessary to protect the confidentiality of sensitive or classified information that may have legal, financial, or personal implications if disclosed. The estimated monetary value, the presence of transient nodes, and the volume of the information are not as relevant as the level of confidentiality, as they do not directly reflect the impact or risk of data exposure. References: 2: CISSP For Dummies, 7th Edition, Chapter 3, page 63.