Now, I do shave only once a week, but I'll happily lay in with the neckbeards on Tolkien stuff.
That said, the fact that movie adaptations exist never bothered me in and of itself. I understand that a lot of things need to be altered for a movie adaptation and I generally try to be kind to them. Truth be told, Legolas being in Mirkwood doesn't bug me at all. It makes sense for pretty much the exact reason Thad mentioned and hell, it's something Tolkien himself might've added if he could have.
What always bugs me is not when scenes are cut or changed around or that the scenery doesn't look the way I want it too. I actually think the LotR movies do an excellent job of nailing most of the visual stuff: costumes, landscapes, etc. I'm not upset that Bombadil was cut, or things like that (though I think he's great and totally belongs, but hey, it's a blindingly easy thing to cut for the movie and a loss that easier to live with than many other things). What bugs me about book adaptations is when the whole theme and meaning is disrupted, undermined, or just thrown wholesale out the window; when characters' personalities undergo wholesale changes; and when the underlying tone of the writing is lost.
It bugs me ten times more with Tolkien, because the guy actually wrote a lengthy (but not THAT lengthy)introduction which is included with every copy of the damn book ever that explains his feelings and themes as clear as day. He was a man who longed nostalgically for a world he remembered from his youth and tried to capture that in a fantasy setting.
It's not something complicated or esoteric. You don't need academics to debate to possible intentions of a long-departed author. The man came right out and said it! Lord of the Rings is the story of the last hurrah of the fantasy world he's worked on his whole life, which doubles as a sort of metaphor for the loss of the supposedly more idyllic world of his youth. I mean, Friday already pointed it out - it's not about battles or swordplay, it's about lingering impressions of nature, about homely meals, and long voyages on foot in true wilderness, it's about the fading away of the last vestiges of fantastic and magical things that were once to great for imagining. It's not a fistfight, it's that last moment just before you completely forget a beautiful dream you had.
But instead we got a trilogy about comedy dwarves and surfing elves and a bunch of characters who kinda go through the motions without really ever having any of the depth that makes LotR more than just a bunch of elves and dwarves and other stock fantasy races beating the crap out of each other. It's why the loss of the scouring does bug me where Bombadil doesn't: It shows in the most visceral fashion that even for the isolated Hobbits in their idyllic Shire, the world has changed irreversibly. It's the clincher, the object lesson for the slow. It's a crucial scene for the theme of the books and a huge and final bit of character development.
The whole failure to understand is disappointing because it seems like no one really understands what fantasy used to mean, back before it was utterly fossilized in the 60's from tropes created in the 30's. They key here is that Tolkien is often lumped in with writers who came in in the 40's 50's and 60's (or later), but really, he fits much more with an earlier breed, with Mervyn Peake, with Kenneth Grahame, with TH Whyte. And even (in a way) with others like Lovecraft or R.E. Howard.
That doesn't mean I want to roll back time to the old Weird Tales pulp days, just that there was a time when all of this was NEW! When Lovecraft wrote of unspeakable horrors and no one had really done anything quite like it, when Hyperborean barbarians walked the dream lands of twisted ancient mythologies, when pixies and fairies were more commonly remembered as they are in say Jonathan Strange and Mr. Norell (ironically, one of the very few truly original fantasy works of our era) as house-spirits or dangerous creatures of active folklore. When goblins and orcs and elves and dwarves as we know them now were almost entirely new ideas - a massive feat of reinvention of Tolkien's, that is so enduring it persists to the degree that it has drowned out everything else. But it was once new! There was a lot of cross-fertilization between these guys in ways that most folks don't realize and they're similar in many surprising ways, but ultimately they each created worlds that were uniquely imaginative and deeply personal - and they shared them. Now that to me is true Fantasy.
What do we get now? D&D sourcebooks and Star Wars Novels, and stories so derivative it boggles the mind to think that there was ever a time when the word "Fantasy" could be taken at face value rather than as hideous mockery of its own meaning.
But I guess movie adaptations are not where you look for originality anyways.
I like stories how about you.