Instagram is a simple platform where users can share photos and receive comments from other users. There are also privacy settings which can allow you to block someone or report for spam. Instagram states that it will not rent or sell a users information to third parties outside Instagram or a group of companies of which instagram is a part of without a users consent. By using Instagram you're also agreeing to its limitation of liability waiver. It will not be responsible if data gets lost or stolen. It does not matter if it's a defective PC or a network breach they will shut down the service and keep data (but not share) for a certain amount of time. I have listed a few ways instagram uses user information below. 

§  remember information so you will not have to re-enter it during your visit or the next time you visit the Service;
§  provide personalized content and information to you and others, which could include online ads or other forms of marketing
§  provide, improve, test, and monitor the effectiveness of our Service
§  develop and test new products and features
§  monitor metrics such as total number of visitors, traffic, and demographic patterns
§  diagnose or fix technology problems
§  automatically update the Instagram application on your device Instagram or other Users may run contests, special offers or other events or activities ("Events") on the Service. If you do not want to participate in an Event, do not use the particular Metadata (i.e. hashtag or geotag) associated with that Event.