I think it's completely and utterly wrong that one person (the advisor) should ever have such absolute power over another (the student). Just as the OP describ

I think it's completely and utterly wrong that one person (the advisor) should ever have such absolute power over another (the student). Just as the OP describes, if the advisor is great, it's fantastic. If they aren't, you are in a world of pain. I don't regret choosing to do a PhD, but I deeply regret choosing my advisor.