I've heard of too many guys getting hurt doing that. At least one fellow had a tooth kicked out. I have an uncle who straddled a wounded buck and brought his knife to its throat, before the buck stood up on it's hind legs and threw him off.

A follow-up arrow is much safer for the hunter, and will bring a swift death the animal. If we're trying to shoot an animal with an arrow in the first place, then finishing it with a second arrow should not pose any dilemnas.