My comment on this:
Other age for reading -- my minimum comfortable average would be 13. I think that it would be a great idea for any site that featured explicit fic to also feature links to proper sex education sites, and emphasize that their fic was not intended to be representative of reality, and that the sex ed sites *are*, and if you are not comfortable with the sex ed sites, then you should not be reading this fic.
I say 13 as my minimum comfortable average and as my comfortable age for a child of my own reading explicit fic because that was the age that I was when I clearly remember having established an interest in erotic literature myself. Not all teens will develop an interest at the same age. I am sure that there are some people who do not show an interest in sexually explicit literature until 18 or after; I am personal friends with adults who were sexually aware and mature (and frustrated!) at eleven.
As I get more fanfic, I will probably start registering my site with net nanny software, because the decision to let young people have access to online erotic literature is ultimately up to the parents, and I feel that software like that is a good way to keep young people who are not sexually mature/aware from encountering material that would really boggle them.
I actually think it would be a good idea for me, and other people, to put the notice on fic sites that if you are becoming disturbed by material that you are reading at any time, to please stop reading it. When I was 16 or so, I ran into a very gross bit of ... well ... I think it was intended to be humiliation fetish erotica. It's a point of pride with me, or at least was at that time, that if I started reading anything, I would finish it, but I couldn't finish that, and the mental images from it squicked me for years. I think reminders that you can, indeed, stop reading it would be a good plan.