Hee :-) At work, I am frequently accused of being contrary just for the sake of it, and right now, I think I am! Because I agree with you for the most part, but not all--some of my best stories were when I had an idea, and just started writing. And in these stories, the writing just *flowed*. It just did. In both, I stopped writing halfway through, with no idea of where I was going with the damn thing, and then ... I got to an end. I got to an end I hadn't really contemplated, but ... it kind of all worked.

Having said that, for the most part, for longer stories--a plot is important, but more than that, I like to have an idea about theme--what am I trying to say with this story? It can be as simple as love conquers all, or don't bite off more than you can chew, or relying on yourself is best, or even that Yohji and Aya are actually very similar and in more ways than they are both pretty--but it should be trying to say something. In fact, all fic, planned or unplanned, fanfic or not, should be trying to say something, should have a point and a purpose--and I find that the fic that interests me least, that is the most forgettable, is the fic that even if beautifully written doesn't even try to tell me anything.