Example: The May 5, 2008 issue of TIME magazine has an article about Stephenie Meyer entitled "The Next J.K. Rowling". I hadn't heard of Stephenie before but she writes young adult, chaste, vampire novels. The article had a vampire illo, and being a vampire fan from way back, I read the whole article.
And there it was, a casual reference to fanfic; the article author making the clear assumption that readers of TIME magazine won't need this term defined:
"Her books are big (500-plus pages) but not dense - they have a pillowy quality distinctly reminiscent of Internet fan fiction."
I do like the idea that fanfic is so commonplace it doesn't need to be defined. Still not too happy about the "pillowy quality" description. I've read a lot of fic that is distinctly un-pillowy, but I do know what they mean. :-)