The revelation of the identity of Deep Throat should throw in sharp relief again the simple truth that the most important stories almost always rely on sources who -- precisely because they are in a position to know key details -- cannot reveal their identity to the public.
Without anonymous sources, there would be little news, certainly no investigative journalism. And what passes as news would tend even more toward news shaped and packaged by powerful institutions and individuals.
The fact that we now know Deep Throat was Mark Felt, whose motivations were probably shaped as much by bureaucratic infighting between the FBI and the Nixon administration as they were by more high-minded goals, should serve to make another point. Most anonymous sources have mixed motives. Many of them have bad or at least petty motives -- backbiting, the desire to gossip or trade in information for advantage, revenge. It runs the gamut.
A good reporter, though, can take the fruit of that poison tree and make it sweet and nourishing by sifting through information to find what is valuable and newsworthy regardless of why it may have come to see the light of day.