From the article:
"Over the past month or so, everyone has been complaining about getting less reach on Facebook. That the algorithm has changed. And that Facebook is now a pay to play system.
Changes have definitely taken place. And as the dust settles we learn more and more about what has really happened, both from Facebook and from the data.
One of the more impactful changes all page admins need to be aware of is that the latest major change in edgerank is now valuing Facebook post negative feedback at a much heavier weight.
This means, as a Facebook page, negative feedback on your content can effectively destroy your post’s reach."