I am an advocate of the Creative Commons. Apart from the pseudo-moralistic arguments, I generally argue that if enforcement costs are high, it is normatively better for the governance structure to favour a more Commons approach. For a private property system will result in its participants spending much of their time and energy on protecting their properties, instead of other "productive/useful" activities.
Technology, of course, does not stand still. While some technology increases enforcement costs (e.g. photocopier, P2P file-sharing, DVD-writers etc.), other reduces them:
A 16-year-old was arrested early Wednesday in a theater showing "Spider-man 2" after a projectionist using night vision goggles saw him using a camcorder to make an illegal copy of the superhero sequel.
The film industry's trade group hailed the arrest and credited its recent initiative to offer cash rewards of up to $500 to theater employees who turn in moviegoers attempting to make illicit film copies.
The fact that it's already difficult to distribute films on the Internet (at least comparing to music), this latest development in technology would imply that enforcement costs within the film industry is relatively low. Compare this with the music industry...the easiest things to copy in the world are ideas, and academia has long been a Commons...