Don’t think it matters whether it’s legal or ethical or whether people do it. What matters is its effect on the therapy, whether the client knows about it or not.

Say a therapist sees a client who has a daughter. Client says they have a great relationship, no problems there. Therapist googles client for some reason, finds daughter’s blog. Client, according to daughter, was a bad mother, maybe abusive, is still. Can you imagine how that affects the therapeutic relationship, whether or not the therapist confessed? Therapy should be what the client brings to the therapy room.

Bottom line is, the client needs to trust the therapist for therapy to work (according to every therapist I’ve ever seen). The therapist does not need to trust the client. Googling the client as in the above scenario does not lead to trust.