In my opinion, there is no way for Universal to hold MySpace or YouTube responsible. I suspect they'll next decide to go after the millions of users that are uploading such files...even more difficult.
I suspect that rather than enforceability in court, what we're likely to see is some sort of digital encryption that makes a piece not only readily identifiable as to source, but perhaps even impossible to decrypt without the key (at least for a week or two, until some 15 year old hacker uploads a how-to to YouTube).
