Do you think that it was Bilbo's fault that Smaug destroyed and killed some of the people in Lake Town?
Chapter 12 ("Inside Information") brings us to a conversation between Bilbo and Smaug. Bilbo sneaks into the mountain alone for a second time to scout things out and to try to find Smaug's weak spot. It turns out that finding a huge, fire-breathing lizard isn't very hard at all. Bilbo finds Smaug asleep on a huge pile of treasure, and inevitably wakes him from his slumber. They begin to exchange banter in this, their first conversation. It's terrified banter on Bilbo's part, but banter nonetheless. During the course of their conversation, Bilbo produces several riddles meant to illustrate his identity when Smaug asks who he is and where he comes from. One of the names Bilbo calls himself is "Barrel-Rider." The crafty Smaug suspects that Bilbo was being helped or was working with the Lake-men, and resolves to pay them a nasty, fiery visit. He also suspects that the Lake-men hired Bilbo in a scheme to steal Smaug's plunder for themselves. After their conversation, Bilbo escapes, and Smaug flies off to raze many buildings in Laketown, and kills many of their men.
Whether or not what happened in Laketown was Bilbo's fault is debatable. His actions were certainly causative, meaning he did not actually kill those people in Laketown himself, but by letting slip the name "Barrel-Rider" he put them at risk. He had no intention of anything bad happening to the men in Laketown, who had housed and fed him at the end of their journey. The question here in its simplest form is "Should people be blamed for unintentional mistakes?" Bilbo certainly meant to cause no harm, and it is unclear whether he could have prevented this from happening while under the influence of dragon-talk (the ability of dragons to trick and coerce people), but his actions caused something terrible to happen.