[color:"orange"]Good points about fleeing there: there are ways to make it less annoying. Though, people will always be looking for ways to exploit any mechanic[/color]
I was thinking of something like a game I don't recall the name of, where sneaking past an opponent gave you half experience points, and if you went back later and killed it, you got the other half. I'd want the full experience for a fleeing opponent, though, since for most practical purposes that is almost as good as defeat.
Speaking of repeated fleeing, though, that should be limited in the interest of realism and reducing annoyance. Animals fleeing more than a couple times in a short while are going to become too tired to flee again, even if they have not been seriously wounded. Perhaps a summoned demon hunting dog could fetch whatever meat, claws, etc the animal may drop when killed, avoiding the necessity of chasing it down at all (assuming it was successful in catching its prey).
For humanoids, if you keep coming after them and they can not hide or outrun you, they should stop running to either attack or try to beg / bribe you to stop. Anyone not fairly confident in their fighting abilities would probably keep a spare invisibility potion (etc) handy, though, if they intended to engage in any risky behaviour.
