The United States Copyright Office always requests opinions before issuing exemptions to copyright laws. The original copyright laws (i.e. Queen Anne's Law) were drafted to protect authors from unscrupulous publishers. I believe the duration of the original copyright was fourteen years.
While the extent of copyright laws has changed considerably over the years, most nations follow the same basic principles, including the notion of a limited copyright. Personally, I think the Sonny Bono Copyright Term Extension Act is out of control. The life of the author plus fifty years was bad enough--seventy years is downright crazy. Given the average life expectancy (in the US) of seventy-five years, that places the duration of the copyright for most works to one hundred fourty-five years. Yikes! But I'm veering off topic. . . .
Anyhow, I do believe that works previously owned by defunct corporations and not transferred to the original creator should be exempted from copyright laws. (Obviously, that doesn't apply to copyrights transferred to a new owner. You all know what I mean.)
Greed, greed is bad. M'kay?
Trev