I've been asking Eugene Volokh to write about property rights and intellectual property for months, and he's finally done it! He argues that intellectual property rights are just as valid a concept as tangible property rights. That's not to say that the existence of intellectual property is good policy, but he thinks the idea is reasonable.
On the other hand, I think that in the digital age intellectual property can be reduced down to the allowing of ownership of pure numbers. For that reason, I think that intellectual property is ultimately doomed.
For my musings on the subject:
1. Ownership -- how can anyone "own" digitally-encoded information? Anything encoded digitally is just a bing number, and how can anyone own a number?
2. Ownership 2 -- more on the same topic.
3. Common Law and Copyright -- can "everyone is doing it" justify violating copyright laws?