This is a REAAAAAALLLLLLY old thread, so I doubt the OP is still listening...
As a writer, I have to tell you that I'd be very upset if you published my work in your book without my permission, and I might seek an attorney for copyright infringement.
Fair enough. But without a REGISTERED copyright, if you want to sue in court, you have to BOTH prove that you actually "own" the copyright and are therefore entitled to enforce it, AND that you have "actual" damages -- provable amounts of money out-of-pocket because of the infringing activity.
You don't have the right to publish someone else's material just because you don't know who wrote it. If someone gave me that excuse, it wouldn't appease me one bit.
Agreed. And copyright infringement is sort of a "strict liability" type of offense, in that even innocent infringers can be held liable. HOWEVER, there is NO duty for someone to exhaustively search to determine whether or not a particular piece of work is copyrighed. This is why the potential remedies are MUCH more severe for infringing a registered copyright than for infringing a nonregistered copyright -- if a copyright is registered, then everyone is considered "on notice" that the work is copyrighted, and therefore could be subject to higher penalties.
If there is no registered copyright, it is not easy (or sometimes even possible) to determine whether a work is still copyrighted without an exhaustive search (at least until they get sued). Therefore, it would be unfair to people to make them subject to pretty serious penalties if they had no efficient way determining whether or not they were infringing.
So, I'm not advocating infringement here -- but I am saying that by checking the copyright office, they are doinf pretty much all they can do, reasonably speaking.
If you are an author and would be THAT upset that someone is stealing your work, then you have no excuse for not registering your copyrights.