How "fake news" come to exist and spread so rapidly

  How has "fake news" come to exist and spread so rapidly? Why do you think this happens? How is "fake news" harmful? What are the long- and short-term effects and consequences of being a consumer of "fake news"? How does it affect each of us? How can we, as consumers and sharers of news, learn to identify potential "fake news" stories? Support your discussion with reliable sources.