I think the answer to this question is not the same for every situation. I agree that Mrs. Spitzer shouldn't have had to stand by her man, but for a different reason than I have heard yet.
I think it is sad that a husband who has erred so seriously, and grievously, would ask his wife to stand there and take the humiliation that rightly is his. It is his consequence, and not hers, to face. If the man is truly repentant, and truly desirous of repairing the rents he has created in their marriage, I think that he would choose to protect her from this painful experience. I don't think a repentant husband would ask his wife to be there.
Of course, we can't really know the reasons behind Mrs. Spitzer's decision to be there. I am not criticizing her at all. Unfortunately, politics has made us all cynical about these events. Was she asked to be there to show that Mr. Spitzer was worthy of forgiveness? After all, who could be more wronged in this situation than she? If she is willing to go on with him, why wouldn't the rest of us?
I sincerely hope that's not the reason behind her presence at the press conferences. I truly hope that Mr. Spitzer is more concerned about repairing the damage to his wife and family, than he is about reviving his career.