I have been looking at this. I am not certain if this is a bad thing or not. I say that because on the one hand, I think it is good that we have a democratization of news sources, both liberal and conservative and anything in between. Back in the pre-internet days, it was the bias of the Big Three news networks and whatever the NY Times was into, which was basically all monochrome news from an elitist New York slant. They often ran all the same stories in (oftentimes) the exact same order. There was no criticism, that was THE NEWS and it was OBJECTIVE (so they said). At least with a Red State/Blue State feed, you have a chance of hearing other voices or stories that the Drive By Media passes on or collectively goes silent on because it "does not fit the narrative." At least this gives the elite media a run for its money.
On the con side, I do understand the "echo chamber" concern. People can get sucked into an artificial world that only reinforces their pre-conceived world views and isolates them from anyone of a contrary opinion. Much like the story about old Walter Mondale who, after getting wiped out in the election against Reagan in '84 (I think he only won his home state of Minnesota and there only by a small margin), and was interviewed some months later about his failed campaign. He got defensive and finally said, "I just don't understand it! I don't know a single person who voted for Reagan!" Interestingly, that happened in the pre-internet days. So, it was perfectly possible before Facebook to get oneself into a bunker mentality.
I am not sure if Facebook is the problem, or it is the People ourselves who are to blame. Even in the days of the Library in Alexandria, Philosophers were notorious for only going into the section of scrolls that aligned with their philosophy of choice. I think the historical annals of none other than Tacitus, he recounts an anecdote of how a Platonist happened to accidentally wander into the Stoic section of library and a riot ensued.
What comes to mind is the famous Adams-Jefferson presidential attack ads.
Talk about polarization. Or look at the propaganda on both sides leading up to the US Civil War. Makes just about anything on Facebook look pretty tame.
I guess my question is: Is there really anything new under the sun?