The Wikipedia on United States copyright law
appears to be a good summary. For example it says:
The purpose of copyright law is to stimulate the creation of as many works of art, literature, music, and other "works of authorship" as possible, in order to benefit the public. The United States recognizes no absolute, natural right in an author to prevent others from copying or otherwise exploiting his work. The copyright laws give authors limited property rights in their works, but for the ultimate purpose of benefiting the public by encouraging the creation and dissemination of more works. The author's interest is secondary to that of the public.
This seems to have been turned on its head in recent years. I don't personally have a problem with a long period of exclusive rights to authors, but it clearly isn't in the public interest for orphan works to be locked up for decades. The problem is how to free up orphan works without over burdening authors. One possibility is for an interested party (e.g. Project Gutenberg) to register a work as orphaned, and if there is no disagreement within a set time for that to take effect. The copyright holder could assert rights later, but the only remedy would be the take down of the (once again) infringing work. I did not read the proposed bills, anyone know what procedure they are suggesting?