Lessig has written a well reasoned article, which mentions the Rip, Mix, Burn ad that I thought was a very strong expression of fair use, but he misses the Church-Turing hypothesis. This is a win for his battle against arcane restrictions on computers to protect content - by emulating the client computer that is allowed to play the content back, the Turing machine defeats the hegemony he fears. It also counters his argument that in 50 years time no computer will be able to run current software. For an encouraging example, he need only look at MAME, the Multi-Arcade Machine Emulator, that will run any videogame from the last 24 years.
A suggested modification to his copyright terms. Twenty years free registration. A dollar for the 21st year. Double this every year thereafter. This would allow Disney to keep paying to keep Mickey out of the public domain, but instead of backroom deals with legislators, it would cost it more and more in copyright fees to do so. To get to 50 years would cost $230, or about $500 Million; to get to 55 years it would be $17 billion. Most works would drop out sooner, but the blockbusters could keep paying for exclusive rights.