Jack Balkin, a scholar on First Amendment issues presents some really interesting criticism of the majority opinion in Eldred v. Ashcroft that may frame new challenges to the DMCA. Ginsberg asserted in the majority opinion that as long as the traditional boundaries of copyright (such as fair use) are unchanged, Congress is free to expend the term. I find the reasoning itself rather odd, since it seems to me that extending the term is changing the boundaries, but Balkin points out that the DMCA rather clearly operates to change those boundaries by restricting fair use.

Worth a read.