Ezra Klein points out that, while journalists like to think of themselves as intrepid sleuths, the best of them are social networkers moreso than detectives.

If you go back to Woodward and Bernstein, Woodward met Felt back when he was serving in the Navy, and the two men bonded over night law school and low-level positions with elected officials.

That’s not to take away from any of their journalistic achievements. Detective work isn’t entirely different — sources are created and cultivated, relationships built and leveraged. But in detective work, sources are sometimes paid, or kept out of jail. Journalists generally don’t have those carrots. And if you’re not going to pay people for their knowledge, then you’re going to need something that encourages them to tell you things they shouldn’t, and that something is often, though not always, the social pressure of a preexisting camaraderie (other candidates are the desire for publicity, or the fear of being hurt in a story).

But sources are never identified as “Warren Buffett, the legendary financier and my personal friend,” or “Valerie Jarrett, a close Obama confidante and someone I developed an improbably warm personal relationship with on the campaign trail.” Readers would dismiss the story out of hand if they were. But that is why Buffett picked up the phone for that reporter, rather than for all the other reporters who put in an interview request.

Presumably, too, this works both ways.  Because the reporter has a warm relationship with his sources, he’s more likely to cut him some slack.

None of this is ideal, of course, since it’s not transparent.  But a strong element of trust is necessary in the source-reporter relationship.  This is yet another cases (described by Shimon Peres and adopted as one of Rumsfeld’s Rules) wherein, “If a problem has no solution, it may not be a problem, but a fact, not to be solved, but to be coped with over time.”