This is probably not the best thread for me to begin my relationship with this board on - but as a psychologist and a tarot reader I can't help but put my two cents in.
Firstly, I have read The Ethics of Caring: Honoring the Web of Life in Our Professional Healing Relationships a few years ago. I can't say that I remember anything ground breaking or particularly insightful.
Secondly, ethics as it applies to psychology is much more involved than would ever be needed for tarot reading. To suggest that tarot readers seek out literature written for therapists is probably overkill. For one thing, clients come to therapy to have their problems addressed with the therapist. They are looking to form a relationship with the therapist and will work together to solve the problems currently being faced. That type of relationship brings about a set of ethical concerns that are simply not relevant to the tarot reader.
I would also like to clarify that the concept of transference (and counter-transference) is an issue that tends to be particular to psychoanalysis. The phrase was coined by Freud himself to describe the sexual tension he believed was present in every client/therapist relationship. It has evolved to refer to not only sexual tension, but also other emotional states directed at the therapist (or at the client in the case of counter-transference). These emotional states arise out of the intimate long-term, sometimes very intense relationship built between the client and therapist. Those therapists who take a psychoanalytic approach are trained to identify and deal with this problem should it arise. In contrast it is not usually an issue that arises in brief therapy sessions (also known as solution-oriented psychotherapy) which, if we have to make broad comparisons, is much more like tarot readings than any other form of therapy.
I agree that we should all behave ethically when dealing with others. I also think the bus driver should behave ethically, and the butcher and my daughter's first grade teacher. I also think the proposal that tarot readers educate themselves as a therapist does is unnecessary. Tarot readings may provide similar valuable insights into issues confronting a client, but what happens next in the therapy relationship bears almost no resemblance to the 'what happens next' in a tarot reading scenario.