While true cephapelvic disproportion occurs, I believe it is an extremely rare event.
During labor, the pelvis widens to accomodate the descending baby.
I also believe that women don't necessarily grow a baby that is too big for them to birth. Biologically, this would be dangerous to the continuation of the species.
There are times when babies are in a less than optimal position for birth, prolonging labor and not fitting in the pelvis well. For more information on this, you can check out: http://www.spinningbabies.com
Induction of labor, especially artifically rupturing the bags of water, can further complicate this issue.
I think that sometimes failure to progress has more to do with putting expectations on a woman to proceed a certain way in labor, and when she doesn't she's deemed to have "failed".
I've seen so many women who had CPD as a diagnosis for a cesarean go on to birth vaginally - most even have bigger babies!
There's no way to tell for sure how a baby will fit through a pelvis (or not) before labor and even then, it's pretty brave to claim that you can.
I've seen one case of CPD that I believe was accurate. This mom held her baby OVER her pubic bone, made it to complete dialation while moving around and baby never descended. However, even though I was witness to this birth, I would never assume that it would happen again under different circumstances.