Patents and copyrights are artificial government grants making the intangible tangible. It's the artificialness that bothers me.
Our culture has come to think ideas are real like real estate. But they are not. They are intangible, and so is information. This feels an awful lot like the meme "ideas are cheap; execution is everything".
As all media become more like raw information--as the cost of transmission and storage of media falls--it will act more like ideas. All that will be left is the government grant to exclusive rights. Thus IP holders lobby governments for larger and larger hammers to beat down infringement.
And anyway, the point of limited IP terms is to allow derivative works for the greater good. I don't hear this greater good argument often enough.
The system is flawed. Perhaps short copyright terms as this article in The Economist suggests are more workable as the information will be fresh. It may also be the only realistic solution when the time comes that infringement is effectively free (as in beer). ["Protecting creativity: Copyright and wrong: Why the rules on copyright need to return to their roots", April 8th 2010, The Economist print edition.]
See also on Hacker News.