Ah, fanon... What catgirl have you not killed?
Personally, fanon was a part of the reason for why I got tired of reading fan-fiction, five or so years ago. The overall quality of the stories was another part, but that's not important right now.
At one time I didn't really mind fanon, since it offered more for a universe (at the time) than the actual series (since the ones that I was interested in were still in their infancy, as far as being translated into English was concerned). However, as I got to know the characters better, in the canon, fanon began to annoy me. Either something didn't make any sense, the information was wrong, or the characters were blatantly OOC. And, as far as I'm concerned, if you're not even trying to keep them as IC as possible, you might as well be writing fiction, not fan-fiction. And, after reading fan-fiction for many years, I found myself at a loss. I couldn't find many good stories, since they tended to stick closely to the canon. And since so few were being made, and I was left to sift through a bunch of rubbish, I got tired of it altogether.
I haven't been able to reconcile with fanon ever since. So much of it is shallow and stereotypical, and I don't want to read the large number of fics that were simply an expression of another's fantasy. And such fantasies seldom bother with much of the canon. Too much fanon just made it hard for me to find a story credible, which is a big thing for me. So, yeah... I don't like fanon. So, once I started to write fan-fiction myself, I stopped reading it. It was time for payback, with my own horrific writing. Mwa-ha-ha-ha-haaaa!