] From the first U.S. copyright statute in 1790 until the
] Copyright Act of 1976, the U.S. had a conditional
] copyright system that limited copyright protection to
] those who took affirmative steps to claim it.
]
] Our tradition of conditional copyright stands in stark
] contrast to what we have today — an unconditional system
] that grants copyright protection whether or not an author
] desires it.

aka abandonware ... check out eldred.cc for more info on this and their proposed Public Domain Enhancment Act that would require
copyrights to be renewed for $1 every 50 years just to keep track
of who holds them to avoid this orphaned-works mess.

Lessig and Copyright renewal...