If people would just read the URL for some of the articles they post... they might have a clue that the reason some of these are "so unbelievable" is because they really are fakes. Do some research, validate your sources are real, and notice the citations (or lack thereof).
Sometimes people have good motives in posting / reposting. But if you are reposting, you should try to make sure it is the truth.
The amount of fake and even comedic blogs that are given the same credibility as verified sources are has increased drastically on Facebook. People need to develop their research skills.