I'm confused as to why you think people would know her due to her role in that, rather than her performance in Fight Club or Harry Potter. She's a pretty well known actress.
I've never heard of John Carter before, but now I have to see it - I have a friend named John Carter.
I'm hugely excited for the Avengers movie - Captain America and Iron Man are awesome, though I haven't seen Thor yet. The sequel to Kick Ass should be good too, whenever that comes out. Oh, and the next Batman movie goes without saying too...
I think I have an obsession with superhero movies. I just haven't seen a really good one in a while, I suppose.
I have never seen Fight Club, and have never wanted to see it.. lol
And it just occurred to me that she was in Harry Potter when you said that, and Very Good in it too.
But why it came out in my post like that is because of the Internet Rabbit Hole that I started from and in... Lol
I was watching Alice In Wonderland tonight and went to the IMDb page to read more about the movie there, and to find out who played the Red Queen.
I Love That Movie, and I watch it every time it is on for the most part.. lol
I didn't recognize it was Helena Bonham Carter with all special effects and that Huge Cranium she has in Alice In Wonderland. lol
I then clicked on Johnny Depp and saw the Dark Shadows link, and then looked to see who else was in it from Alice In Wonderland.
If you have never heard of John Carter before then that means you don't know about the books, Which Are Excellent.
http://www.johncarterofmars.ca/, from the Edgar Rice Burroughs, Inc webpage.
http://en.wikipedia.org/wiki/John_Carter_(character), wiki page.
Same author that wrote all of the original Tarzan books, that all of the movies come from, http://en.wikipedia.org/wiki/Edgar_Rice_Burroughs.
Here's the trailer for the "John Carter" movie: http://youtu.be/6Rf55GTEZ_E
Awesome! I will be looking forward to seeing that movie for sure.
Thanks for posting that.

EDIT:
A quote for the You Tube page, from a fan of that video:
John Carter, The Warlord Of Mars,
Could Read Men's Minds 18-Years Before The Shadow.
Was Surrounded By Naked Women 20-Years Before Conan.
Flew In Advanced Sky-Craft 22-Years Before Flash Gordon.
Was Able To Leap To Tall Buildings 26-Years Before Superman.
Conquered A World Devastated By Environmental Disaster 80-Years Before Al Gore.
John Carter Is The Man!
Yes Indeed He Is! Lol