In the last few months, I read a lot of spec fiction. I also watched a lot of movies based on spec fiction, including movie adaptations of books I read. When you translate media in that fashion, there is always some drift from the thrust of the story. In some ways I think it's okay; in others, my cynical mind assumes the worst. Allow me to elaborate.
(Muse: Oh this should be good.)
Like I said, some migrations hold up better than others. I have not seen Hunger Games all the way through but from the parts I have seen, it is a faithful translation. 300 was almost a frame-by-frame reshoot of the comic. Other movies add in extra material, scenes, or even characters; the recent Hobbit movie did this and it did not really affect the integrity of the story, save for reducing the film to a glacial pace.
I've heard some complaints about movies like Clash of the Titans, that have dicked with classical Greek mythology. That doesn't bother me, since mythology, per se, isn't owned by anyone and is subject to interpretation. The main elements of the tale are there, even if it is a hybrid of the tales of Perseus and Bellerophon. Besides, what harm can it do? Today's society is so ignorant of the classical world that it's not like this will ever hold them back from something. It's dead knowledge.
Oh just wait, this is where it gets fun, because here is where I have the problem.
There is a certain money-grubbing element in the entertainment industry that is quick to latch onto a success story and try to siphon from it, leech-like, for its own gain. In this case, I would be thinking of the upcoming World War Z movie. From what I can see from the previews, it is not even remotely related to the "source" material. It's Brad Pitt in a zombie apocalypse movie – maybe with decent action, effects, and a soundtrack. Perhaps I would even pay to go see it. But it does not appear to resemble the book at all. In the book, the narrator was a reporter, who gathered stories after the crisis was over. Pitt's character is in the midst of the action. Fast zombies versus slow zombies. And on. So why call it World War Z, if not in an effort to cash in on the success of the book? If they had called "Zombie Movie #85" would it generate as much buzz? (Actually that self-parodying title might have, a la Zombieland.) I see a very cynical effort behind that, rather than letting the movie rise or fall on its own merits, someone along the way tried to predispose it for success. That leaves me with a sour taste.
So where is the line drawn? What differentiates between a little poetic license and an abomination of an adaptation? I dunno. That's what makes this a fascinating subject, as it is always up for debate-slash-reinterpretation. I doubt it's a linear distinction for anyone, but probably more of a matrix: a combination of personal resistance to the idea and a strong affinity for whatever source material is being lifted. Is this even worthy of discussion?