This fucking guy's got more screentime than half the dwarves.
Spoiler alert: this plot device ain't getting old anytime soon.
He calls for the dwarves to take up arms and fight. The Goblin King is knocked off the platform by Thorin. After an extended action scene, Thorin's Company fights its way through Goblin Town. The Goblin King blocks their exit, and snarls "What are you going to do now, wizard?" After Gandalf disembowels him, he says, "That'll do it," and dies. The bridge collapses, and the Company fall several hundred feet to safety. Bofur opines that the situation could have gone worse, then the Goblin King collapses on them.
The Book: The Goblin King, who is described as "a tremendous goblin with a huge head," demands to know who the dwarves are and what they are going in his kingdom. Thorin immediately offers up his name, then tries to assure the Goblin King that they meant no harm, and were simply seeking shelter from a storm. He goes on to say that they are on a trip to visit family that reside east of "these truly hospitable mountains." One of the goblins calls him a liar, holding up Thorin's sword. The Great Goblin, recognizing Orcrist, gives a howl of rage and orders their deaths, rushing forward to kill Thorin himself. Just then the cavern goes dark, and a great fire explodes into a tower of sparks that sends the goblins running. Gandalf's sword strikes the Great Goblin dead, and Thorin's Company takes the opportunity to escape. Dori carries Bilbo on his shoulders as they follow Gandalf. Gandalf and Thorin fight a few guards during their escape, but never quite reach the "epic battle" scale of the movie. The goblins then decide to try something different; they snuff out their torches and sneak up on the dwarves. This is how they snuck up on Dori and grabbed him, causing Bilbo to fall into blackness.
What difference does it make? The motivations of the goblins are quite different in book and film. In the novel, they're simply suspicious of the dwarves at first. They may be rough with their prisoners, but they only become truly violent when they realize that the leader of the Company is wielding a sword that is known for killing goblins. The Great Goblin decides to kill them much quicker in the book, due to the bounty placed on their heads by Azog the Defiler. This, of course, is not present in the novel at all, since Azog isn't in the novel. There is no "final fight" with the Goblin King; he dies pretty early, and pretty easily. The goblins never try to change their tactics.
Thorin is treated a little more differently, too. In the movie he is obstinate, refusing to talk at all until Ori (who, it's worth noting, is not the youngest dwarf - Fili and Kili are younger) is threatened. In the book he is not only a great deal more meek, but kind of a coward, too - he lies to the Goblin King to avoid his wrath, and makes a fawning comment about the hospitality of the Misty Mountains.
I'll say this: the Goblin King's "That'll do it!" is the worst part of this movie. It's cringeworthy, painful, stupid, and makes me squirm uncomfortably every time I see it. I honestly can't decide why it's in this fucking movie, or what Peter Jackson was thinking. He is literally changing the works of esteemed author J.R.R. Tolkein and replacing them with lines out of fucking Jason X.
Clearly, that's just the Great Goblin's favorite movie.
While I didn't mind the change in how Bilbo got separated from the rest of the group, I have to say, a small part of me was disappointed that the movie didn't have any scenes of him being carried on Dori's shoulders. It's not a big detail, and honestly may have been difficult to pull off on film (especially if we're to take Bilbo Baggins seriously as a helpful member of the group), but I was kind of hoping to see it. Oh, well.