I did a little googling, and found this site, which has lots of entertaining-looking reading material:

The Fanfic Symposium: Columns by Topic
http://www.trickster.org/symposium/coltopic.html

These are four articles on the site that I read, that are relevant to your question. Some of the others may be, as well.

Hurt/Comfort: a Confession and a Celebration by Renae
http://www.trickster.org/symposium/symp55.html

We Always Hurt the Ones We Love by Lucy Gilliam
http://www.trickster.org/symposium/symp13.htm

Why On Earth Rape Fics Exist by Emmuzka
http://www.trickster.org/symposium/symp109.html

You're a Spiteful Bitch! Why I Hurt the Ones I Love by Cyndiana
http://www.trickster.org/symposium/symp145.html