There's a lot of chest thumping in this thread.
If a bad guy poses enough of a threat to use deadly force in the first place, I can see the logic in trying to finish the fight and neutralize the threat -- but a self-defense shooting gets investigated like any other homicide when it is all said and done. The more squirrely and questionable the actions in the shooting, the greater the potential for a DA and/or a Grand Jury to consider it was a bad shoot -- and I'd guess that entry wounds in a bad guy's back at the edge of your property line would be a red flag for investigating officers, the DA, etc.
Does that mean shooting the fleeing bad guy is always the wrong answer? No -- as other people have noted, you can wargame and what if the question to death and get either a never shoot or never-not-shoot scenario. But people who think the law is going to just give them a pass for defending themselves with a five round rhythm drill into a would-be burglars back probably need to give this topic a lot more thought about the potential for criminal and civil actions arising from the shooting. There's a pretty high suck factor in the notion of saving your stereo from a strung-out meth head only to shoot and kill him and then have his equally worthless family win a multi-million dollar wrongful death suit against you and spend the rest of your life sending them a check every month.