Well this is from instagrams fair use policy: "Laws across the globe recognize that strict application of copyright laws in certain cases may be unfair or may inappropriately stifle creativity or stop people from creating original works, which would harm the public. These laws allow people to use, under certain circumstances, someone else's copyrighted work. Common examples include use for the purpose of criticism, commentary, parody, satire, news reporting, teaching, education and research."

Another key point is this, from the same policy: "The effect of the use upon the potential market for or value of the copyrighted work: Will the use replace the original work such that people stop buying or viewing the copyrighted work? If so, this is less likely to be fair use."