Right, firstly let me explain a little... Hopefully without resorting to personal attacks, insults and assumptions - unlike your good self...
Facebook doesn't simply gather information about me, from me. When I had my FB account, it had my email address, my name and a partial date of birth. I didn't include my school, my college, place of work, address or any other such information.
However - my friends and family aren't so careful with the information they include. So, you get instances of my sister, for example, requesting that we become "family" members on the site... So, Facebook now have an albeit unconfirmed snippet of information about me that I didn't enter.
From that information, they now know that the connection between her and me is more than random, and should they wish, they can grep her account, and find where the rest of my family live... Hang on - they all live in one part of the country, I live in another... Did the whole family move? Or did I?
Now they can guess where I lived... A quick search of the usual "ex-school friends" who HAVE put which school they attended, and now they can have an educated guess at what school I did... And they can work out what year...
And if they know what year, they can calculate the year of my birth.
That's a quick example of how connections between people can be used to glean more information than is posted by an individual. It might be no more nefarious than wanting to sell adverts at me - but that's not the point. You can bet your final fiver they do data analysis along those lines.
Now - moving on from Family and my birthday - the final straw in the coffin of mixed metaphors was when they turned on the Facial Recognition and made it Opt-OUT instead of IN. I know you can turn it off, and I did - but it got me thinking again about the bullshit privacy problems they've had for the last 18 months... And then I had a typical "tech support" conversation with me old Mum who wanted to know how she can delete a photo of her that someone else put on Facebook - well, short of asking the person to delete it - you can't. You can only delete the tag.
After some careful consideration over the weekend, I decided that these points coupled with a general weariness of Facebook were too much in comparison to the benefits I gain from using the service. So I quit.
I really do hope that's ok with you.