Before the current regime of copyright maximalism, copyright applied only to text and its printing and reprinting rights. Following a discussion on the Creative Commons mailing list I have placed the copyrights of my characters, concepts, plot elements and worlds under the CC-by licence.
It is well known that most creators of commercial worlds effectively cannot and would rather not enforce noncommercial fan art (fiction, videos, games, etc.) of their worlds. But why not also allow such works to be sold commercially, be filmed, or otherwise make a profit? Let a Thousand Flowers Bloom!
For example, following Terry Pratchett’s death, his daughter Rhianna Pratchett, who is his inheritor, announced that she closes her father’s Discworld franchise for commercial and official sequels. But why not allow commercial and unofficial sequels, prequels, fan art, forks, crossovers / mashups, etc.? Put the franchise under CC-by and tell the fans that they can build fan art above it as they please and request (not force - see Saladin-style) that a donation be made to the Pratchett’s estate, if there was a substantial profit.
Yet another case of franchise copyrights abuse is that of “Harry rotters: Warner Bros cracks down on Potter fan festivals in US” where Warner Bros (who bought the rights to the Harry Potter franchise) demanded that Harry Potter conventions / festivals not use any names from the books. I have no idea how this demand will be “good for the people”, help make the world a better place, and/or “help someone get laid”. It just seems like a dick move by some overzealous lawyers.
And now for the other side of the coin, according to the English Wikipedia, International Talk Like a Pirate Day (which is a fun holiday which I celebrate on the Internet, and have also created some related fan art), had become successful in part because its copyrights or trademarks have not been enforced, which led to a "viral" growth.
It is likely that creators of commercial franchises would benefit more by making their worlds, characters, and concepts unrestricted, rather than being territorial around them. Some of my Internet friends agree with me that Spaceballs is a better film than the original Star Wars trilogy. However, being a parody and therefore fan art, it builds upon the original work and depends on it.
We are all standing on the shoulders of giants, so why not let others stand on ours?