I think what throws gas on the fire in these discussions is the use of the term 'ethical'. I'm guessing that a lot of guys have different definitions of what that word means. I use it in the sense of knowing what is the risk of wounding the deer as opposed to outright killing it. If there is a high risk of wounding, then it's not an ethical shot.

With that in mind, it's obvious that some shots will have a higher risk of wounding for hunters that are not as skilled at taking that type of shot. Running targets, long range shots, having a weapon you're not that familiar with, aspect of the target (especially with a bow) all increase the difficulty of the shot. Therefore, every hunter has to know his limits and only take those shots that you feel have a high probability of killing the deer (and conversely, a low probability of wounding it). If you can routinely hit a small, moving target like a deer's head, it's ethical; for hunters that only shoot a few times before season, however, it's probably beyond their skill level.

In other words, it's unethical to fire off shots you know are very highly likely to just wound the animal (e.g. unloading unaimed shots across a field at a running deer); if you're confident in your ability to limit the risk, it's ethical.

In the end, it's up to each hunter to know where he stands on that skill gradient.