I turned mine off and never provided facebook with my phone number because that's how people find you.
People fail to realize that when facebook shows you the "people you may know" suggestions what its doing is looking at your contacts and phone number, then it check it against the database to see who provided facebook with that number and then suggest them to you.
Ive met females at bars that gave me fake names but real numbers only to see facebook later suggested that I know this person and wouldn't you know it, their whole profile is public, where they work, where they hang out, etc. Even random hookups with women only to see Facebook suggest them as a friend to me 24 hours later and I find out that they are married or have a family.
The best one was where I was with a female and facebook suggested the friend connection, I look at the profile and I see pictures of her that look like sex ad pictures you would see for camgirl ads. I did a image search on one of the pictures and it took me right to backpage where she was selling herself. I confronted her and she flips it around on me and calls me a stalker and a creep......thanks Facebook
This is the same way your employer or manager can find you too, all they need I your phone number in their contacts and as long as you provide facebook with your number your namager can easily find your profile and see what you do in your spare time or anything you may say or do to become a risky employee.