Dean is right that "fake news" is a meme that was invented to attack alternative news sources - those that aren't on the left. And, it is a ploy to encourage self-censorship, like the concepts (or anti-concepts) of "politically correct", "trigger words" and "micro-aggressions" - it is an attempt at controlling speech and shutting down avenues of thought that don't agree with progressive agendas. Recently, progressives, knowing that many of the heads of social media companies are sympathetic to their cause, invoked "fake news" as a way to encourage the social media company to "filter" out news that they deemed "fake news" (and that would include some news that wasn't fake, just opposition to progressive goals - like any story about faked data in the climate change debate).
I think that this focus on "fake news" is still new enough, and non-objective enough, and dishonest enough in its biased use that it can be taken litterally and turned against all attempts to make up stories that favor some political agenda. Turn it against the left who are in the middle of an orgy of anti-Trump "fake news" attacks.
Regardless of who started the "fake news" meme, or what their motivations, it is a useful concept when taken litterally and applied rationally to all who attempt to make up news as opposed to report news.
The main stream media has failed to maintain journalistic standards and have become propoganda sources, and at the same time we have the unregulated net (and it SHOULD be unregulated) which has some extremely irresponsible people who make use of anonymnity and any lack of consequences to publish things they know are false. That is just the way things are now. With time, cultural and economic structures will arise in the marketplace to provide a way to vet news sources (although that relies on some intelligence among consumers, and in the political realm that's in short supply now.)