Question

Woodward and Bernstein kept their main source a secret for over 30 years. What is the importance of newspaper reporters keeping their sources confidential?

Answer 1

Without keeping their sources confidential, many of potential informants will be discouraged from giving the information.
The most important information came from someone that worked deep inside the incidents and decided to act out as a whistleblower. If the information about these informants is exposed, Their life could be in danger.