How many times have you seen a photo in Facebook's News Feed that encouraged you to "Like/Share" if you agree or "Comment" if you disagree (e.g. a math puzzle). The company will try to slowly eliminate these, as it announced in an official announcement that it has upgraded its News Feed algorithm to understand which Pages are filling the feed with "spam" content in order to gain Likes.
Once such posts are detected, the page's ability to display its content even to those who have "Liked" it will be degraded (the so-called "Reach" will drop). Also, posts that have been posted repeatedly in the past or contain external links that lead to websites with advertisements will not be displayed. It was a long time ago..
Source: techgear.gr

