I agree that this trend demands ongoing attention and analysis, but I would suggest that the scandal, and church positions on some of the "hot button issues" may be playing a bigger factor than the question's answer would suggest.  For the younger nones, they may be sincere that these were not THEIR motivating factors.  But I suspect that what we're seeing in the loss of the younger, is that they've grown up in an environment wherein their parents and extended families have not been supportive of being Catholic.  The reasons for the loss of that generation may well be the scandal, and those church positions.  Stated differently, perhaps the survey folks were asking the right question, but to the wrong generation.

This problem is likely to grow, for with each non-church marriage, the "none" position propagates into  future generations.