That’s the whole point Sherz, as long as it can be proven who wrote something it really doesn’t matter.
The onus is on the artist to keep any manuscripts, lyrics and sequencer project files as well as any audio but the latter category can only ever amount to prima facie evidence as demonstrated by US law.
Yes, that’s tended to be my thinking too. I don’t think I’d really have any trouble proving my ownership of my work. I firstly register all my work with my performing rights organisation before uploading. And that, plus I have all my working files, Cubase projects, other associated documents in my possession, along with perhaps say testimonials from those in my household that have endured my mixing sessions! - hopefully all that should be enough! 
And I’m also thinking you never really truly know until that ownership is actually challenged in a court of law, which is really why I was kinda curious if such a case had ever come up in the past and if so what the outcome was. 
A court of law would be very reluctant to allow such matters to proceed because the onus is on the original writer(s) to prove they had written a piece of music, and were there to be evidence supporting an actual version history (not tags on audio files or envelopes) then expert opinion would be easier to ascertain, ie a Musicologist.
This whole hubbub over copyright of video and TV shows is a bit rich considering that in most cases there is advertising supporting a network or cinema and thus royalties are being paid and to target individuals through an ISP is really without base particularly when for example a television show in NTSC is copied to PAL and loses frames in the process thus the quality is inferior and technically it isn’t the same thing eg redigitized media.
I just read the following:
While copyright registration does not prove ownership of copyright, this legal presumption of ownership and validity constitutes a prima facie proof (on first appearance). Consequently, in cases of infringement the court will presume that the ownership of the copyright and the registration is valid and will shift the burden of proof to the defendant to disprove by showing with sufficient evidence the falsity or invalidity of the allegation.
I can see it could all potentially get quite messy!
Issues of copyright (p) aside, with the onus of proof being on the defendant; while anyone can “register” copyright prima facie it is meaningless if the evidence cannot be supported and it would be a very costly gamble for anyone to try and register another’s work simply because they’d have to be a part of the evolution of a song, which is where any case before a court would likely begin between friends who both had a hand in the writing of a song, which could be attributable to anything but most likely a creative deficit somewhere along the line or falling out, ie sleeping with someones’ wife 
I remember Joe Satriani had a conflict with Coldplay recently, don’t know the outcome.
No doubt someone got screwed… probably not anyone’s wife though… 
Does the EU recognize USA copyright filings?
Or would someone in the US be smart to file not only with us.gov at the link above, but also with some EU equivalent?
In that case, it could well become a “human rights” issue.
Check out the Berne Convention. Each country party to it is required to recognise automatic (unregistered) copyright in any of the 164 countries that have signed up. The US is also a signatory so I don’t understand how that sits with the plagiarismtoday article.
OK, thanks for that, Duck.