Hard data, credible sources are what make a strong newspaper story - not a convenient message from someone who would be embarrassed if the story were untrue (something which is at least as hard to disprove in this case as it is to actually prove)
In this case "someone" is a double Pulitzer Prize winner, and what was said was something of a nature that means the editor in any reputable newspaper will demand hard evidence, i.e. he will have the names of all the sources, and confirmed with at least some of them. If the story is a fraud (possible, look up Jayson Blair), the editor would have to be in on it, and it would be a larger scandal than the story itself, which really just confirms what everybody already suspected.
The story is as good as investigative journalism gets.
And yes, reputation matters a lot in journalism. Jayson Blair is a life coach today.
It's a sketchy system, but it's the best we can get if we want journalism to remain investigative (though we may already be losing that battle).