There's been a fair bit of howling over the lack of realism in the movie. Wouldn't this be a case where staying true to the book makes the movie look even more like a fairy tale?

From the book: "Then he [Gandalf] set one alight with bright blue fire, and therw it whizzing down.... Then another came and another, one in blue flames, one in red, another in green. They burst on the ground...and went off in coloured sparks and smoke."

I think a spectacular display of multi-colored fireworks right as Thorin and Azog are having their initial taunting and stare-down session might be a bit distracting. Spectacular, perhaps -- I do enjoy a good fireworks display myself -- but I think a bit understated rather than overstated perhaps works best here. I could be wrong!