I remember someone created a P2P file sharing system that used 'munges' of files to create blocks of data by themselves that have no meaning (a bit like http://monolith.sourceforge.net/). These blocks were then transferred around the network, and people could claim "I'm not transferring files, I'm transferring meaningless blocks of data".

Sure, but (and I'm not a lawyer), intent of law is just as important as the literal meaning of law. Cases play out this intent and add to the corpus of knowledge as case law. So if you did write a program to generate all the data in the world, I'd imagine people would look at your intent, rather than just what you literally did.