Most Facebook users think they see all their friends in the news feed and everything is okay, they just think some are just not posting. Well it might not be the case.
Facebook use algorithms, whether it be to select what is the top news, what friends to suggest or what photo memories to show but the most disturbing fact is that there is also an algorithm for the people who appear in your news feed whether it be in "Recent Post" or "Top News". In fact that old friend you haven't spoken in a while could be not appearing in your news feed when he/she is posting.
I studied the algorithms behavior for two months be observing without doing any test but by simply doing business as usual. What I noticed is I was always seeing the same persons, which were the persons I wanted to see but there were missing some so I was wondering. I checked on the Facebook application for iPhone and iPod Touch and there was no filter, no algorithm, I was seeing everyone. But on the website I was not getting any post of the people I was adding even after posting a message to their wall for the new friendship. So I asked myself what the algorithm was considering for making someone appear in your news feed and noticed some important key points.