What Defines Dark Magic?

[psychodudeneo]

No: HPFGUIDX 53527

I was just thinking.  Dark Magic is always hailed as being evil and 
wrong.  However, who decides what is Dark and what isn't?  Curses, 
one would think, would all be considered Dark Magic.  However, many 
of them are not.  There are only three curses we know of that are 
defined as Dark Magic (the Unforgivable).  The rest seem perfectly 
accepted in everyday use.

Can Dark Magics be used for good?  Or is it inherently evil?  One 
would think that with one of the overall themes of the books being 
how you use what you have, I would think that you could use them for 
good, but that doesn't seem to be the case.  There are 
certainly "good" spells that could be put to evil use if the 
practitioner has an evil mind, so why not the other way around?  
Where is the line drawn? 

Obviously, killing someone with a curse is a bit different than 
causing carrots to grow out of their head - but think about it.  
Could a spell/curse that causes one's head to suddenly sprout 
vegetables be put to a positive use at all?  It's just very confusing.

Durmstrang has a stigma about teaching it's students Dark Magic.  Are 
they wrong to do this, or are they just letting the young wizards see 
more options?
- Psy