Every company tracks you. From what you purchase at target, to broad pattern behavior tracking on the web via ad companies, I think most people know their being tracked at various stages for various reasons.
However, is it bad that target knows I like to buy grass fed beef? Probably not. It reveals some things about me, but I am far less concerned, as are most I imagine. This same mindset is what fuels people when they don't care what FB/etc is doing. Not that it's right/wrong, but I think people don't care who knows about their lunch or catpics. Thinking that's all that FB could gain out of it.
Humans in general are really bad at thinking long term. Nothing bad happens immediately when you sign up to FB, when you post personal information, when they sell your data, etc. For a lot of FB users, it might be 20 years before they regret their actions. That's just a hard feedback cycle for people.
For example if you drive a bicycle and eat beef, most likely you have a certain income, have a certain family type ( you use same IP!! ) , which means you might have a certain political view and concerns. And this is where targeted manipulation is active, they can drive you in a certain direction. Psychology at it's best.
This is how you win an election.
Giving my information to FB/etc though? That's another story.