I agree with >>20 re: GPL-like licenses. They rely on the very same form of control over users that they purport to attack. (Also, the GPL has a lot of restrictions in it that have nothing to do with sharing software at all; read it sometime.)

I think a limited form of copyright is necessary for movies and for books that are the result of substantial research. Maybe computer games that require a lot of artwork and level design, as well. Other things are either cheap to produce (e.g. music) or will be made by volunteers just because they want to (e.g. software). Maybe a very light sprinkling of copyright on such things can help, but it also has the potential to hurt, too, as it is doing in its current excesses.