Seemed like a safe bet at the time.
The Book: Bilbo meets Thorin's Company right outside the Green Dragon Inn. Balin was looking out, but the rest were already on their ponies as Bilbo was running late. No mention is made of any contract. Thorin orders Balin and Bilbo to get on their ponies (which Bilbo has no objection to), and Bilbo complains that he has no hat, handkerchief, or money. Dwalin tells him that he "will have to manage without pocket-handkerchiefs, and a good many other things." He does, however, provide Bilbo with a dark-green cloak and hood. Gandalf arrives late, having still been at Bilbo's house, with a bunch of handkerchiefs as well as Bilbo's pipe and tobacco.
What does it matter? Having Bilbo meet the dwarves on the road, instead of at the inn, has no repercussions on the rest of the story. Nor does Bilbo's lack of handkerchiefs, or the color of his clothing. The addition of the "betting" scene was a humorous touch that added a layer of depth to the personality of the dwarves (individually, and as a group).
My Opinion: I much prefer Bilbo's appearance in the movie than in the book - the red and green give a distinctive appearance that "green on green" rather lacked. I don't have any strong opinions about the change in meeting place, but I can see how one might get frustrated or annoyed by it, especially if they were looking forward to seeing the Green Dragon Inn. It's another example of Peter Jackson changing something that simply didn't have to be changed. This time, however, I don't really care about it.
One thing that did irk me, however, was the change in which character provides which lines. Peter Jackson plays fast and lose with the characterization of the dwarves throughout the movie. This in itself isn't a big deal (though, personally, I'm disappointed that my favorite dwarf from the book is known to my friends solely as the one who said "the wine has a fruity bouquet"). So little personality is given to each dwarf in The Hobbit that it doesn't matter how Peter Jackson chooses to divide their lines in the movie. Gloin's "he looks more like a grocer than a burglar" is fine coming out of Thorin's mouth, for example. Taking away Dwalin's generosity in the book and giving it to Bofur, sure. But it irks me that one of Dwalin's important lines is given to Gandalf, a character who already has more personality and characterization than all of the dwarves combined - in both book and movie! It's hard enough making each dwarf interesting and unique, but it's going to be even harder if you give their lines to the wizard.