In her answer to another [question][1],  Slytherincess mentioned this from a chat with JK Rowling :

> From a web chat: 

> > Jaclyn: Did Lily ever have feelings back for Snape? 

> > J.K. Rowling: Yes. She might even have grown to love him romantically (she certainly loved him as a friend) if he had not **loved Dark Magic so much**, and been drawn to such loathesome people and acts. 

> SOURCE: http://www.the-leaky-cauldron.org/2007/7/30/j-k-rowling-web-chat-transcript ... :)

What is it that drew Snape so strongly to Dark Magicâ„¢ that JK says he loves it? 

The other dark wizard's seem to have a fixation on power, and merely use Dark Magic as a means to an end. Even their favouring purebloods is,  in part a play for power over the 'less powerful' mudbloods. 

So why is/was Snape in love with Dark Magic?

  [1]: http://scifi.stackexchange.com/a/8673/3804