Arguments Against Copyright
Copyright results in a weaker incentive at creativity
"The evolution of copyright from an occasional grant of royal privilege to a formal and eventually widespread system of law should in principle have enhanced composers' income from publication. The evidence from our quantitative comparison of honoraria received by Beethoven, with no copyright law in his territory, and Robert Schumann, benefiting from nearly universal European copyright, provides at best questionable support for the hypothesis that copyright fundamentally changed composers' fortunes. From the qualitative evidence on Giuseppe Verdi, who was the first important composer to experience the new Italian copyright regime and devise strategies to derive maximum advantage, it is clear that copyright could make a substantial difference. In the case of Verdi, greater remuneration through full exploitation of the copyright system led perceptibly to a lessening of composing effort." [1]
Artificial Scarcity - Unlike physical property, intellectual property is not scare. Infringing on copyright, unlike theft, does not deprive the victom of the original item.
Internet enforcement is impossible - The cost of enforcing copyright on a global network designed to efficiently reproduce information is unreasonable. Innovative technologies like peer to peer file-sharing software and digital libraries will be hindered by 20th Century copyright laws.
Freedom of knowledge - Copyright restricts the right to an education and the right to communicate freely. Commercial restrictions on knowledge (like academic journals) impede social progress.
Further Reading:
Against Intellectual Monopoly by Michele Boldrin and David K. Levine
Free Culture by Lawrence Lessig