I think the judge made a wise ruling. Intent has long been an important part of the criminal legal system. Civil cases live by a different set of standards, but in a situation like what the RIAA is trying to accomplish, I think this makes sense. Simply have a folder of music that "can" be publicly accessed by others, on it's own doesn't prove that the poster put it there solely for the purpose of illegal copyright infringement and distribution, regardless of what we all know to be true.
Jack