I chose to focus on Instagram; I don’t have an account on this site so I was curious to know what their policy was. I was unaware that they were recently bought by Facebook, and would be collaborating with them about their terms of service, and privacy statement.
Instagram is just like most other social sites on how they will use your information. Instagram says that they will not sell your information to companies out side of Instagram, “or the parties that they work with” i.e. Facebook, so if you didn’t have a Facebook, but had an Instagram, Facebook now has all of your information and can use it however they like. Any pictures, or content that you share will become public information, and if and when you choose to delete your profile, your information will still be searchable and can be found on the archived page through the Instagram site.
If Instagram ever chose to sell to another social media site, (other than Facebook) that site would now have to honor Instagram’s old terms of service and privacy statement.
You should continue to check the sites privacy statement and terms of service, as “they may change periodically.”