because facebook is a network which is managed by CIA, and not only CIA, there are many more agencies those are tracking you, including all of your activities, and furthermore, facebook does not care about your privacy, last year, facebook sold 250+ million users data.
Seriously, this is no longer a new thing, almost everyone knows that Facebook is no longer safe. Even your account can be hacked. I have seen this happen a lot of time to people; hackers will take over their account and change their passwords, and then start to use that account to deceive their friends and all those of rubbish. Sometimes they will hack it and delete every piece of information you have saved there.
I already know that Facebook is selling users information, and not just to CIA as you have said, also to advertisers. I have seen officers show up at someone's house due to a comment on Facebook, lol, that's when I learnt to respect myself. Well, I am not the type of person that gives out every information about myself on Facebook. Even my name is not the complete real one.