You may have noticed a link I have in the sidebar to Fashion Incubator, Kathleen Fasanella's fascinating site. I check her posts often, and there's always something interesting. Her latest post is called A Question of Thoracic Shaping and in it she is asking whether readers have the type of thoracic shaping she is discussing. This may sound arcane and boring, until you grasp that what she is really talking about is why bras do not fit. Now, who can fail to sit up and take notice of that? No one I know. I suggest you take a look at her post, which includes many photos and diagrams, and see whether you think you fall into her "egg shaped" category, rather than the "standard" oval. (It may not be really standard, but it's what all the bra manufacturers appear to be designing for.) Egg shaped seems to basically mean that you're wider from front to back than side to side, although I'm sure I'm oversimplifying it greatly.
I have read the post several times, and I cannot really decide whether I am an egg or not. I seem to have at least some of the characteristics, but I'm just not sure. I find that it's rather unsettling to realize that I am not as familiar with my own bodyshape as I thought I was. I know I've never been completely happy with bras, but who has? Anyway, go; read the post, and comment. She has a plan to help those with egg-shaped torsos, and maybe everyone else along with it.