Another thought came to mind while rereading the book: Peter Jackson made a huge deal out of each time Frodo put on the One Ring in The Fellowship of the Ring
and how Sauron felt its presence. Now, I don't remember how that was depicted in the book (but I don't think it was quite like how we saw it in the film), but Bilbo's frequent use of the One Ring is quite nonchalant. That's no surprise considering the book was written long before the trilogy (even if he did edit the "Riddles in the Dark" chapter to make it more aligned to the trilogy) and hadn't fully developed the One Ring and such.
My question is how will Peter Jackson depict Bilbo's use of the One Ring? He uses it frequently (escaping Gollum, sneaking up on the dwarves, escaping and fighting the spiders, freeing the dwarves from the Silvan Elves, etc.) with no ill effect. Will Peter Jackson tie this in with the rise of the Necromancer?