The nightmare for everyone involved in any creative industry is that one day the ideas will dry up. More particularly for the international market, it is what happens when all the remakes have been remade, the original books and plays adapted, the sequels drifting off into painful repetition.
It's a niggling doubt that is present, however distant, in the justified celebrations of another success. The fantastic performance of Spider-Man 3 at the world's box offices once again defied the critics. Spidey showed he could be as much of a smash in downtown Seoul as in Des Moines, Iowa. And so, Spider-Man 4, 5 and 6 seem like a no-brainer.
Michael Lynton at Sony said earlier this month that he believes such blockbusters hold the key, not only to the studio's future, but to the next generation high-definition DVD system on which his company is putting so much faith.
The term blockbuster needs a little clarification. Any film that makes a mint can of course be counted as a blockbuster. But the definition can be narrowed to mean a product that has deliberately set out to find themes and ideas with enough global marketing pull to justify a huge budget and global release.
The monster successes of franchises such as Lord Of The Rings can hide the fact that such properties are thin on the ground. Following the comic book adaptations of recent years, the repertoire looks close to exhaustion. Spider-Man, Superman and Batman are the only true global brands. Television properties that play in multiple territories are also rare - The Simpsons perhaps being the obvious exception. Few other television adaptations have come close to the mark. The cop series and comedies of our youths rarely reach across borders and even less so bridge generation gaps.
In terms of books, the really big ones have disappeared: Lord Of The Rings, Harry Potter, The Da Vinci Code. Extending a franchise has its own inner tensions, such as the stars getting older. Even Harry Potter, whose genius has been that the character gets older with each book, is running into difficulties. It's hard to imagine even Tobey Maguire keeping up the illusion of the teen.
So what exactly are the next big surefire brands' The answer is in the hands of a growing breed of what we might term film alchemists. The alchemist is searching for that magic ingredient that unites the global audience. Let's not forget that box office gold has been created from seemingly the basest metal over recent years: Pirates Of The Caribbean springs to mind. The alchemist is unfairly dismissed as seeking the lowest common denominator. In reality, finding any kind of denominator for a fragmented global market is a tough call. The work of the alchemist is in some ways a world away from the film-maker who increasingly wants or is forced to satisfy a clearer audience. Some bank on the self-belief that their vision will find its way to like-minded souls. Others have a clearer sense of a specific audience, united by individual tastes or nationality. What unites both ends of the industry is the need more than anything else for originality.
The thought comes to the forefront at Cannes where so much industry-changing genius has made its mark over the last 60 years. It's easy to see such events as conservative protectors of grand old traditions - and there is some truth in that view. The writers behind the screenwriters manifesto (see page 6) have reason to believe that the view of film as the creation only of auteurs leaves out too much of the history. But scanning through the historic programmes of Cannes and other festivals, what really stands out is change, particularly the opening up of world markets.
Film is so much richer now with the range of cultural influences from around the world. Out of those contacts, a generation of film-makers - alchemists or individualists - will find the rich seams to create tomorrow's cinema.