Well, one problem with this is that most authors don't hold the rights to their works and it's not possible to get their permission. I think if all I had to do

Well, one problem with this is that most authors don't hold the rights to their works and it's not possible to get their permission. I think if all I had to do to publish a homemade video to Weird Al song was get Al's permission, it would be pretty sensible. But he signed away his right to a corp who will fight to the death to extend and exclusively control the work. The authors would have a much better sense of whether a derivative work robs them of income or is reasonable. Also, high quality work is expensive. And in the old days, it probably took decades to recoup costs when books were prohibitively expensive. But when a film these days make 100MM in its premiere, I think we need to seriously shorten copyright terms.