Everyone makes their own boundaries; you and me, therapists, everyone. There are some discussions on why one way is better than another but it is what works for us as individuals; you cannot have a love affairs with your therapist if they do not want it and if both want it, it is probably going to happen no matter what others say or punishments from professional organizations, etc. There is no "law" saying these things cannot happen, just professional organizations that do not want people licensed to have relationships with their clients and, here, if you are not licensed, you often cannot practice/work in the field you have chosen.