DrCrowTStarwars said:
One thing I do think they screwed up with in giving the Archenstone some sort of magical hold on Thorin that he had to fight off like the Ring. In the book it was just simple greed and the fact that in the warrior culture that he came from you don't give up anything that is yours to someone else because that makes you look too weak and Bilbo ended up being the bridge between the warriors culture of the Dwarves and the peaceful town culture of the river people.
The Arkenstone had some degree of magical hold on Bilbo, at least, in the book (according to what I read just yesterday). I haven't seen the movie, so I don't know how it's portrayed, but it seemed like more than simple greed in the book.