As of March 1989 it is unnecessary to make a claim for copyright in the US.

Yes...., but that doesn't mean it's valid to willingly make an incorrect claim [1]. Furthermore, if you sue for damages if there has been a copyright infrigment, you greatly reduce your chance of collecting damages if you didn't make your claim.

[1] With that statement, I'm not saying that putting a Copyright © 2004 statement in a book that's published at the end of 2003 is an invalid claim.

Abigail