As you’ve indicated, whether copyright infringement has occurred is not based on registration (though that would be strong evidence, aye?).

However, as I understand, assuming a court rules in one’s favor that compensation for lost royalties is warranted, the maximum compensation one can receive is based on the lost royalties from the date of registration (or maybe, of the mailing of the registration forms). This is detailed legal-stuff that I may be remembering incorrectly.

If I am correct though, the implication is:

As long as you aren’t making any money on stuff you’ve recorded and there’s no one infringing on your copyright, it isn’t necessary to be registered. So, if your band is still in the garage and you aren’t making any money because no one is listening to you yet (or an agent’s artist is still in the studio and there’s no way anyone is stealing this hypothetical author’s material yet), then its not time to sweat the registration.

For these folks, hopefully the time comes when registration is very important.