I agree with sirthumper that the "fantasy" and "fiction" perspective shouldn't be lost. Personally, underage isn't my thing but I have no problem with someone writing about it or reading about it. The main thing that would stop me from writing about forcible acts on an underage girl is the remote possibility that someone with different values would read it, like it and act it out. I couldn't live with myself if I provided the motivation behind such a thing. I realize it's a rare possibility and even if it did happen its unlikely I would ever know about it. Still, the easiest way to avoid the whole thing is simply not to write it!

I've even thought about writing of a 15 or 16 year old girl who is ahead of her years and uses sex to blackmail men.