The original U.S. copyright law, hard-coded into the Constitution, is for a 14 year period of exclusive distribution, with the option of a one-time renewal. This was originally intended for authors, and I think that it's entirely fair. Were this law still in effect, everything in the U.S. made prior to 1984 would be in the public domain.
However, I'd like to point out that when the section on copyright was originally drafted, there was no such thing as free distribution. It cost money to duplicate anything, and so copies had to be paid for to recoup on losses. The law was designed to prevent others from profiting on a new work, giving the artist time to collect on the the time and effort s/he put into it. It was never intended to limit distribution, but rather to encourage it, as the creator had nothing to risk by sharing his/her work.
With the advent of the internet and computing in general, non-profiting distribution has to be considered a separate case. In many cases, works are being distributed to people who either aren't going to or aren't allowed to buy said works, representing exactly zero loss to the rightsholders, but a great deal of free advertising. Any serious artist would be overjoyed by that prospect.