Some are fake news from fake news sites, which spread scurrilous rumors and made up stories.
And perhaps this should be alarming for Facebook. When people realize that the junk in their "feed" is mostly made-up stories, lies, crap, junk, and advertisements, the incentive to go back online may diminish. Already, it seems as though younger people are finding another outlet for their spare time.
If Facebook turns into an old folks home, where FoxNews-watching types exchange scare stories about the "Wal-Mart Slasher" it will turn into a joke.