Right now in CS 60, we are learning about logic and basic circuitry in the run up to learning ISCAL. AND, OR, and so forth. One of the logic functions we learned was XOR, which looks like this:
X1 X0 Y
0 0 0
0 1 1
1 0 1
1 1 0
It's the same function as binary addition, minus the carry. The other cute thing about it is that it's completely reversable: XOR together either of the inputs with the output, and you get the other input.
Someone else noticed this quirk and decided to apply it to the whole copyright mess with a little program called Monolith. The program mushes together two "element" files into a Mono file. Combine the Mono file with either of the original elements, and you get the other element file. Theoretically, the program could be used for filesharing--by distributing a Mono along with Jason Rohrer's public domain default Monolith element, one could *theoretically* get around the text of copyright law.
How? It's obvious to any non-computer scientist that the Mono is just a transmutation of a copyrighted work, easily reversed. This workaround would never hold up in court. However, when you consider the files on the level of binary, and take a strict interpretation of copyright law, a Mono file fails to qualify for legal protection either on grounds of being a derivative work or on being the work itself. (The article goes into the details as to why--go read.)
Monolith certainly isn't a legal recourse for filesharing. At best, it could evade record labels' attempts to watermark or copy-protect their music--making filesharing safer for its users, if no less illegal. But I think it illustrates pretty well how outdated American copyright law is. The law is written for an analog society. The society it's trying to govern is digital. What it means to "copy" or "distribute" something is very different now. You just made a "copy" of this website just by looking at it. And making "copies" of larger and larger files is only getting faster and easier. The law needs to change so that it can make sense of these facts.