A recent post to The Book People Mailing List, which is hosted by the UPenn Online Book Page, suggests that the US Copyright Office is recommending US Copyright law be changed to allow the use of orphaned works. What I find most interesting is this last comment:

As I read this, then, someone running a completely noncommercial online book site could look for the owner of a book they want to post but that is (or might be) still in copyright. If they do the right things but don't find a copyright holder, they could go ahead and post the book online. As long as they promptly take the book down if the copyright holder later shows up, they're not liable for monetary damages.

The poster notes that they've just skimmed the report and that their interpretation may, ultimately, be wrong and that a closer reading of the report is needed.

You can find the report at http://www.copyright.gov/orphan/.

via Archivalia.