The Free Expression Policy Project of the Brennan Center of Justice (at NYU's law school) has just released a report titled: "Will Fair Use Survive? Free Expression in the Age of Copyright Control".
To get kind of technical, as C.E. Petit has noted:
Keep in mind that fair use is not a privilege. It is instead an affirmative defense to an accusation of infringement. (Unfortunately, neither the statute nor the courts are very consistent in treating it as such.)
That said, the (quite reasonable) concern expressed in the study is that the culture surrounding copyright and trademark enforcement is having chilling effects on the exercise of the right to free speech. Those interested in the legal issues surrounding fan-created content and intellectual property may find it worth a look.