Have you seen Facebook's [Satire] Text? For the past month Facebook has had the "satire" text in front of links in the "Related Articles" box as a Beta Test.
Facebook decided to test this because users were constantly wondering if what they were reading was a true story, or just bogus.
I have to admit, when I saw the posting of Robin Williams passing, I had hoped it was a hoax, but as we all know it was true.
I have noticed that the only time I have seen the tag work has been with articles from theonion.com which is widely known for its false stories.
It seems the only time the tags appear are when you click on a false story that shows up in your feed and later return to Facebook to only find another false story with a "Related Articles" box noting "satire" related articles. See my example below:
Some folks have seen these results and have asked if this was another Facebook Experiment. The answer is no; it is just a Beta test to see if it helps users decipher what is real and what is purely a prank to give readers a good laugh or stir controversy.
My guess is that Facebook is trying to give you a hint that the article that landed in your feed is possibly fake. Which still leaves you asking the question, "Is it REAL or is it FAKE?" If it means that much to you, you must always do your homework and find out if what you see is true or not. After all, just because it's on Facebook doesn't mean it's true.