Jake, too large a meal for the size of the snake can cause regurgitation, which is a very bad thing for a snake. Not that I enjoy it, but regurgitation isn't so much a big deal for us humans. But it can cause bigger problems for our snakes.
Also take a look at my previous post about emaciated snakes. Too large of a meal in a snake that has no gut flora can kill the snake. The reason for this is that the snake can't digest the meal, and it rots in the snake's stomach. I know this from experience.
Steve