Ned Snow, Assistant Professor at the University of Arkansas at Fayetteville School of Law, has made "Proving Fair Use: Burden of Proof as Burden of Speech" available on SSRN.
Here's an excerpt:
Requiring fair users to prove the fairness of their expression threatens fair use‘s very purpose—to protect speech. . . . Facing a hefty punishment for losing the uphill battle of proof, fair users self censor. The burden chills the speech that fair use is intended to protect.
Judicial placement of the burden with fair users represents an attempt to foster expression by safeguarding copyright. The attempt has failed miserably. The burden represents heavy-handed patrolling in the marketplace of ideas. Trying to punish those who steal, courts are punishing those who share. They have turned an open emporium of exchange into a highbrow boutique for the wealthy. It is therefore time to construe fair use as it was originally intended—a doctrine that defines the scope of copyright‘s rights. It is time to restore the burden of proof to plaintiffs. It is time to return to the traditional contours of copyright that will cultivate creativity.