I'm in school for my Masters to become a T, and this is something that is brought up often. I've never heard a professor say that it's against the client's best interest to contact their T outside of session. What they've said is that it is important to let your client's know up front what your policies are regarding contact. If a client becomes too demanding you need to address this in session and explain what your boundaries and expectations are regarding contact. Obviously no one shouldn't give out personal cell numbers or emails, but then I've heard about T's that do, which baffles me.

I think the problem with some Ts are afraid of getting in a situation where a client goes overboard and is dependent on contact like Sierra pointed out. They are afraid to have the conversation if a client goes overboard with the contact so instead they go to extremes. They set rigid blanket policies about no contact at all or are overly permissive and allow too much. All people have boundaries, friends, family, co-workers, etc., and there are many people who don't respect them. So it is important in therapy for a T to be warm and flexible with some contact, but also be firm so that clients who may struggle with boundaries can perhaps learn from it. Therapy really isn't the one place where we can do anything we want, when we want. That's not reflective of real life and I isn't treating clients as responsible adults.