This thread needs some posts. I'm not sure that your above example would bother me all THAT much. I mean, there are certainly good traditions and bad traditions.... As long as Gumpas and his slave trade is portrayed as evil and corrupt and Caspian fixes it, I don't think I'll complain about the scene too much.

what specific moment in VDT do you fear will be changed/twisted in the movie?

I'm not sure that I have a specific moment. The top one would probably be Eustace's undragoning. But as many people on this forum can attest to, I'm far more bothered by character changes instead of scene changes.
I'd really hate to see Caspian at odds with the Pevensies for most of the journey. Yes, there are moments in the book that they argue like Deathwater Island and when Caspian tries to go with Reep to Aslan's Country, but it'd be so like filmmakers to add in a power struggle that lasts throughout the movie.

I fear that the voyage will be turned into a save-the-world thing instead of a journey of discovery.
I fear that the dialogue in the last scene will be cut because some might think Christianity is inappropriate.
I fear that the undragoning of Eustace will not be shown as it is in the book where Eustace tries to remove his skin but can't. It speaks volumes that he hates his own skin so much.
I fear that Caspian and Ramandu's Daughter will kiss. That would kill their romance.
And lastly, I fear that Edmund and Caspian will have a power struggle.

I hadn't thought of that, Clives Staples Sibelius. I can see where that might happen. Great, one more thing to fear.

I think I agree a lot with "daughter of the King." I fear a lot of the same things she does; but to try to put my biggest ones in more of my own words,
1., I fear a general restructuring of the book (like PC or Eragon, f.e.),
2., I fear it will still carry traces of LOTR epic stuff (like the last two movies)
3., (I'm using her words here) that Edmund and Caspian will have a power struggle
4., that the Christian points will be taken out.

I think this sums up most of it.

Alright Here's a list from most feared to least

1. Any character change
2. A change that is annoying and unnecessary; the kind that makes you go "why did that have to happen". (i.e. Susan and Caspian)
3. An added character

Wow! I never thought about that change, C.S.S., but I can definitely see it happening. *shudders*

- I hope that they don't add new major characters. That would be so annoying. Anyone who is there that is not meant to be that takes up gobs of screentime would just be a bad, bad addition.

- The LOTGK in any part of the movie. Come on, seriously?

- If they change up Caspian and RD's romance that'll make me upset as well.

1. Giving Ramandu's daughter a name.
I'm sorry, but for me that would just ruin it... Lewis kept it secret for a very good reason, and to cross that line would be... undesirable.

2. Non-canon romance
Just... no.

3. Eustace's dragon scene.
So many ways to totally and completely blow it, one way to get it right (and that being following the book of course).

4. Changing the theme of the story
Self-explanatory...

'Kay, I think that covers it for me, and yes, they are in order of preference.

I try to not worry about the movie, but it's one thing they can't change.

The last scene when the Pevensies and Eustace talks to Aslan. I absolutly love that! And that Aslan goes from a lamb is important for me as well. I'm also worried that they will change their lines so it goes wrong if you know what I mean? But I think they will make a good movie and I hope so

1. Any sort of relationship between anyone.

2. Trying to make someone look bad or selfish like they did to Peter in PC.

3. Eustace as dragon.

That's all I can think of right now and yes, it's in order of most feared to least feared.

Generally I feared much the same as everyone above - conflict with Edmund and Caspian, leaving out or changing of end scene , messing up of dragon scene but I think I've read too many rumours and now I also worry about the rumours of an underwater battle with the mer folk, Lucy having a crush on Caspian and some mysterious quest being added as the reason for the voyage

The changes I fear, in order from most worrisome to least:

1. Two words: "Unfathomable fate"

2. Major character changes (i.e. Eustace is a good kid from the beginning. This is an extreme and unlikely example.)

3. Unnecessary mushy stuff (meaning anything outside of the Caspian/RD 'ship, or making the Caspian/RD 'ship too strong; adding mush scenes)

4. Deleting islands (combining is OK-to a point). All of the islands are important to the feel of VDT.

I think that the one thing that I fear most is not a bunch of changes to the plot itself but a change from the feel of the book. It has to have an exiting and wonderment feel about it. The kind that has to do with discovering unknown places. It has to be a more of "everything is alright at home so lets just go exploring" kind of feel. If it doesn't have that then something will be missing for me.

I am with fantasia_kitty, if they change the scene with how Eustace becomes a boy again I will be sad because I really love that scene. It is a very powerful part of the book with Aslan pealing the scales off.

I don't want Caspian to ask about Susan, he needs to be thinking about the voyage. And when he meets Ramadu's Daughter, well, hopefully its sweet and not one of those awkward scenes.

1. I don't care about the un-dragoning scene TOO much. What I DO care about is the conversation between Edmund and Eustace afterwards. It's my favorite part of the entire series.
2. Ramandu's Daughter must be nameless. I will accept no other option.
3. No Suspian.

I think that's about it...

I'm really actually not too worried about the changes they'll make. All I want are the main themes to stay intact, and for the character's to stay themselves.