Indeed it is. Everyone owes it to themselves to consider what the risks and rewards of their own situation are. And the things you mention can and do happen.
I also think a person with some awareness can do sensible things to protect themselves from some of these situations without changing the main focus of their strategy - which in Zen's case is to save her marriage.
People in her position can and do consult with attorneys, for example, so that they are not taken advantage of should things eventually not work the way they want. I don't condone naivete' on anyone's part. If your goal is to save your marriage, however, I think you also have to be careful to make sure that your defensive precautions don't reach the point where they undermine your main goal or cause you to live in a toxic state of fear.
As far as I know, no one has the power to "disallow" an affair. No one has to or will stop an affair if they don't want to. The other partner can chose to voice their suspicions or confront their spouse with the evidence as the case may be. Yet, for reasons I outlined in my last post, I believe there are at least some instances - depending on your goals - where you would not want to do this.
