What's With the Talking Donkey?

Reading the story of Balaam, one wonders why it is included in the Torah. Why didn't God simply forbid Balaam from going to Moab the second time he asked? It turns out that Balaam gets mentioned as a bad example all the way from Deuteronomy to Revelation. In this, he serves to emphasize that sex is very often the hook that is used to draw people away from God and in to idol worship.