By now I am used to this certain routine: I get to chat about the wonders of the Internet with somebody; through this and that, I explain my fears of the likes of Google, Facebook or any of the other companies tracking my every online move; and in reply I am asked, "So what? What are you so afraid of?"
Well, the following clip from the American 60 Minutes provides some background information. Amongst others, it also demonstrates some of the reasons why we should all be afraid of the total decimation of our privacy.
In case you cannot be bothered to watch through the clip, I will let you know it shows how online data brokers allow the highest bidder to buy people lists. That is, lists of people with certain traits: gay people, people with certain religious inclinations, people with political attitudes, and people in certain financial conditions.
Call me a weirdo, but I do not want to find myself on someone's list without having a saying on the matter. Whether you are an atheist or a young earth creationist, whether you are a left winger or a right winger, the choice of whether others should know about it should be yours and yours alone; it should definitely not be made through some online aggregator who notices what your Facebook likes are and what books you buy at Amazon.
People may still say "who cares". But today they chase the gays; in the history of recent countries considered to be the bastion of democracy we have people being chased for their political opinions; the list can continue. One day, it would be your turn to appear on a list you do not want to appear on.
Be prudent. Look out for your online identity, because sooner or later it would affect your offline identity just as well.