The most recent publication of "fake news" was debunked so quickly it was all over before many of us had heard the first account. This particular fake news involved alleged sleazy behavior on behalf of Donald Trump. See Hours Before Trump's Press Conference CNN And BuzzFeed Hit 'Fake News' Bottom and Buzzfeed’s Trump report takes ‘fake news’ to a new level for rebuttals.
If Buzzfeed editors knew it was fake, or at least questionable, why did they publish it?
Here's a possible explanation -- they knew and took advantage of the theory of "Belief Echoes." The theory is described in Belief echoes: The persistent effects of corrected misinformation. Here's an excerpt from the abstract:
However, through a series of experiments, I find that exposure to a piece of negative political information persists in shaping attitudes even after the information has been successfully discredited. A correction—even when it is fully believed—does not eliminate the effects of misinformation on attitudes. These lingering attitudinal effects, which I call "belief echoes," are created even when the misinformation is corrected immediately, arguably the gold standard of journalistic fact-checking.
In other words, fake news can shape attitudes even after it's been proven fake. No wonder some partisans are so eager to publish it.