"People don't realize how all this is shared." - Steve Vondran
Your name, address, your birthday, what you like, where you go (geolocation), what you spend, etc., is all collected (aggregating), shared, and even sold (data mining).
"Instagram does not claim ownership of any content that you post on or through the service". - Instagram/Facebook
However ... Vondran points out that while you may claim ownership of your content, Instagram retains the right to use your content (royalty free), subject to the privacy policy that you agreed to, and that they can change their policy at any given time.