As of the 16th of January 2013 Instagram with be putting implace a new privacy policy. This will mean all you data will be shared with it’s owner Facebook. So now information such as cookies, log files, device identifiers, location data and usage data will share with businesses they are legally a part of.
“We may share User Content and your information (including but not limited to, information from cookies, log files, device identifiers, location data, and usage data) with businesses that are legally part of the same group of companies that Instagram is part of, or that become part of that group (“Affiliates”). Affiliates may use this information to help provide, understand, and improve the Service (including by providing analytics) and Affiliates’ own services (including by providing you with better and more relevant experiences). But these Affiliates will honor the choices you make about who can see your photos.”
Basically reading the above section from the new policy it sounds like to me that they are using this information to better target advertising. The real question is does this mean your information will be in the privacy nightmare that is facebook.
The instagram blog claims that this is going to be a great thing for you, reducing your spam and relibilty issues.
“Our updated privacy policy helps Instagram function more easily as part of Facebook by being able to share info between the two groups. This means we can do things like fight spam more effectively, detect system and reliability problems more quickly, and build better features for everyone by understanding how Instagram is used.”