If Strong AI turns out to not be possible, what are our best expectations today as to why?

I'm thinking of trying myself at writing a sci-fi story, do you think exploring this idea has positive utility? I'm not sure myself: it looks like the idea that intelligence explosion is a possibility could use more public exposure, as it is.

I wanted to include a popular meme image macro here, but decided against it. I can't help it: every time I think "what if", I think of this guy.