social media - the hidden persuaders

I recently set up a Facebook Group for our local village community and in doing so canvassed people's opinion as to their willingness to join the group. Our community is a mixture of all ages so this was quite a useful exercise to gauge opinion. The results are hardly scientific but it is probably fair to say that the younger generation (18-40) is more disposed to social media than its more senior counterpart. However, a regular comment made was one of concern about the dangers of social media in general and Facebook in particular.
I have often remarked that, in an age when you hear more about data privacy and invasion of personal information and rights than ever before, the majority of people are quite willing to expose themselves (metaphorically but sometimes literally) to world scrutiny. Sadly I feel that this majority does not appreciate quite what happens to their information once they click 'send'.
Firstly, anything they write or 'post' has the potential to be shared instantly around the world.  You can quickly delete a post but, unless you are double quick, the chances are that it has already been shared either directly or indirectly and every share leads exponentially to more shares. There is NO WAY of deleting it entirely from the internet. But, even if people are wise to this risk and are still prepared to take a chance, very few are likely to be aware of the mass of other information about them that is automatically captured by social media. This data about you (called metadata) can include anything that Facebook knows about you from the day you joined. This includes all your friends and family, places you have visited, your likes and dislikes, your political and life style choices and so on.
Facebook and other forms of social media - typically Twitter, Google and You Tube - run what are called algorithms; bits of code that analyse all this metadata. The resultant huge databases about social media users are then exploited by advertisers to populate your personal Facebook stream with adverts tailored exclusively to you.  This is what pays for 'free' social media.
But it is not just adverts that are a worry. Facebook (and others) use these algorithms to tailor everything that you see on your Facebook 'news feed'.  Over time, you will only be presented with items in your feed that particularly play to your personal preferences or views.  And how do they know your preferences and views?  Easy. They determine these from the groups that you join, the people you follow, the other posts and comments that you 'like' and 'dislike' and so on.  Again over time, any contrary view or opinion will be hidden or given far less prominence in material presented in your feed.  
You might say 'Well, that's no worse than reading rubbish in the newspapers.' But think about it for a moment. You can choose what papers (and pages/articles) to read and what items to ignore.  You can't with Facebook because your news is personally selected for you.
In a very recent book by Roger McNamee called 'Zucked. Waking up to the Facebook Catastrophe' (Mark Zuckerberg of course being the CEO of Facebook), these algorithms are called 'filter bubbles'. Now consider that Facebook (with its apps) controls the personal data of nearly 3 Billion people around the world.  That is 40% of the world's population of 7.5 Billion. (figures corrected 25 Feb). Now you can see what influence social media has. The book goes on to say that the use of Facebook data (by outsiders NOT by Facebook themselves) probably contributed in large measure to the election of Donald Trump and to the result of our own Brexit referendum.
Have you woken up yet?????