I read "The Hobbit" long before I watched the films so I can safely say that the screenwriters and producers had modified the script to lengthen the narrative into a feature-length film (or three of them, in this case). I remember the White Orc being only briefly mentioned in the book but in the film his role was made into that of major villain and Big Bad Guy.
Also I think Rhadagast the Brown plays a more prominent role in the film than in the original children's story book that Tolkien wrote.
Don't forget the romance between the elf woman and the dwarf guy! Gosh, that part made me feel so sad! It was so disappointing, wish they hadn't added that. A very disappointing ending for me. I hate it when screenwriters do that kind of things... add characters that are not even supposed to be there. I found Rhadagast to be such an interesting character, even more the one from the book, but it was nice to see him in the film as well, hehehe.
Yeah, that made no sense at all. I was pretty mad on that part. Why can't they just stick to the book. I don't remember all of that in the book, why add it to the film. It was senseless to have them in love with one another and then he dies in the end.