On the issue of honorifics for people with PhDs, I'm generally happy to call people whatever they want to be called. But my own preference is as follows. I lean toward reserving "Dr." for medical doctors, and I find it weird having that title applied to me, since I just have a PhD in a social science. I tend to prefer "Professor" as an honorific for PhD holders, though I realize that gets tricky when you're talking about PhD holders outside of academia, or at institutions where people are picky about academic ranks (recall the controversy over whether Obama lied in saying he was a "professor" of constitutional law since his job title was just "instructor"). I find it especially weird if I'm called "Dr." in a context where my advanced knowledge of Mary Douglas's cultural theory is not relevant. So for example, when I'm in for a checkup, the parties involved are "Dr. Chung" and "Mr. Danielson"/"Stentor." But if my physician were to decide to take a cultural geography class at Pima Community College, we'd be "Mr. Chung"/"Daniel" and "Prof. Danielson" in class.