Confirmation of key facts has never stopped being an important pillar of journalism.
However, the decision to publish or broadcast a story is often not determined by the availability of conclusive facts.
The juicy details of a story, (well aligned with driving up newspaper sales perhaps?), at times can't wait for comprehensive due diligence, given the fickle nature of news.
That's why a right of reply must always be accorded to those adversely mentioned.
The only problem then is that, a whole complement of obstacles could arise, ranging from court injunctions, non-cooperative news sources, decoys, to even the killing of stories.
This is often after the intervention of internal higher forces in the managerial or editorial chain of command, acting on pressure/inducement from external 'sources' with vested interests
So you either choose to publish and be damned, or hold the damnation and have no news for your target audience.
There is though, a small time-tested principle advocating for the use of multiple sources, to corroborate details of a story, before going to press.
To go ahead and publish the fact that a story was based on a single 'reliable' source... is self-incriminating, and counter-indicative of the credibility of a news organisation.
Now that is a 'source' of concern!.