You know I used to travel for business and from time to time alone with married woman. After the meetings I would go out with them and enjoy their companies and have fun with them. Never had an affair with any of them (not even in thought) but just keep good memories of that.
Now if the thread is about married men going out with other women to have an affair then this is a completely different story. In this case, it is up to the cheated spouse to draw the red line. As they say: You want to play in my playground then follow my rules. If their is no lines this would just get worst and worst.
Sorry if I misunderstood the thread topic.