Imagine a court trial in which a witness is not required to testify in person or reveal their identity. They can simply have a lawyer read an anonymous letter on their behalf.
In such a trial, how could the judge or jury determine if what the witness said is true? If the defense cannot question the witness, then the accused would no longer have a fair trial.
Such is the case with news stories based on anonymous sources.
Many stories with anonymous sources do serve the public interest. An anonymous source who is honest (and accurate) can bring things into the light that were hidden in the dark. This can lead to more people coming forward to tell the truth.
Nevertheless, when a source for a news story can hide behind a wall of anonymity, there is often no way of knowing if what they are saying is true. They can say whatever they want and suffer no consequences if they are lying.
Even if they are not lying, anonymous sources can still be wrong. The truth can only be known by considering all the facts, and an anonymous source may only have a limited understanding of a situation.
Not all anonymous sources have noble motives. If they work for the government, they may go to the media because they disagree with the polices of the party in power. They may say false or misleading things to damage the reputation of a politician they hate.
Whatever the motive of the accuser, the consequence of a news story with an unnamed source is the accused is limited in their ability to defend themselves.
They are also judged in the court of public opinion, and often with lasting damage to their reputation. (In the court of public opinion, an accusation often equals proof of guilt.)
Case in point: CNN has published many negative stories about Donald Trump based on anonymous sources. Because Trump cannot challenge his accusers directly, his only defense is to say that the story is “fake news.”
If a negative story about a politician cannot be proven false, a certain percentage of people will believe it is true. This can have a negative impact the politician’s approval ratings.
Media companies have a financial incentive to publish “fake news.” With Facebook and Google dominating the advertising market, media companies are struggling to survive. Stories with anonymous sources are often sensational stories that will attract readers. The more clicks, the more advertising revenue it will generate.
As long as a story with an unnamed source cannot be proven false, a media company has little to lose in publishing it. A story with an unnamed source is often about something that happened behind closed doors. However, it is often difficult to prove that something did not happen. Hence, stories with anonymous sources are often risk-free to publish.
Stories that are based on unnamed sources should be read with a high degree of skepticism. When a source for a news story is not willing to reveal their identity, the story should be considered nothing more than a rumour. Sadly, many people will automatically believe such stories to be true.