Here's something I hadn't considered:
One early darknet has been termed the “sneakernet”: walking by foot to your friend carrying video cassettes or floppy discs. Nor is the sneakernet purely a technology of the past. The capacity of portable storage devices is increasing exponentially, much faster than Internet bandwidth, according to a principle known as “Kryder’s Law.” The information in our pockets yesterday was measured in megabytes, today in gigabytes, tomorrow in terabytes and in a few years probably in petabytes (an incredible amount of data). Within 10-15 years a cheap pocket-size media player will probably be able to store all recorded music that has ever been released — ready for direct copying to another person’s device.
In other words: The sneakernet will come back if needed. “I believe this is a ‘wild card’ that most people in the music industry are not seeing at all,” writes Swedish filesharing researcher Daniel Johansson. “When music fans can say, ‘I have all the music from 1950-2010, do you want a copy?’ — what kind of business models will be viable in such a reality?”
That's from anti-copyright guru Rasmus Fleischer in the lead essay of this month's Cato Unbound. But that's a good point. Suppose you can put everything on Lexis, or every movie ever made, on a thumb drive. What are they going do, ban Fed Ex? Thumb drives? Fleischer seems to think copyright is hopeless, but that in the short term, the attempt to police violations could really harm civil liberties. I suspect he's right.