The Mythgard Institute recently posted a podcast about Thorin (previous editions have been about Thror and Thrain). Here is the summary from Mythgard.org:
Prof. Corey Olsen and Dave Kale finally get to the heart of the matter and discuss Thorin Oakenshield. They compare his different portrayals across The Hobbit, Appendix A of The Return of the King, and different versions of The Quest of Erebor and analyze how they may be combined and adapted by Peter Jackson’s team in the upcoming The Hobbit films.
This episode can be downloaded as an mp3 from their website. I’m happy to see it covers many of the things I have pondered about the character. Mr. Kale and Dr. Olsen are (obviously) well-informed on the topic, and attempt to support their speculations with available evidence. Among other things, they focus on how material outside the main Hobbit text (namely “The Quest of Erebor”) may impact character relationships in the story, particularly in terms of heightening early tension between Gandalf, Thorin, and Bilbo.