A misconception that this example could cause it that galaxies are found only in the outer part of the universe. Galaxies have various shapes, oval, spiral, double spiral (like our own galaxy) and explaining them like raising could make someone thinks that they are only in the outer part of the universe, like raisins. Beside from this fact, the example is a clear method to explain the expansion of the universe, and how galaxies are going apart from each other.
