A couple of dictionary definitions of voyeur:
"a person who enjoys seeing the pain or distress of others"
"a person who likes seeing and talking or writing about something that is considered to be private"

By these definitions, every therapist I've talked to has been a psychological voyeur. One could argue that they do not enjoy this, rather they just "want to help". But I think it's both. I think an essential part of the psychology of wanting to be a therapist has to include some fascination with the private lives of others, and a need to gratify this. There is something lurid about a person sitting in a room all day long gorging on the secrets of others. Doesn't make it good or bad intrinsically, but let's not kid ourselves that therapists are paragons of healthy boundaries.