This post, and the ensuing comments, raise some interesting questions. What really is the "line" between appropriate and in- in an academic relationship?
When I first started at varsity, I was utterly in awe of my lecturers. My parents had really built up to us what it took to achieve a PhD, and it made me really excited, and also a little afraid, of the whole process. I called everyone "professor" or "doctor" as appropriate (or sometimes not. I called several doctors "professor". I prefer to err on the side of flattery, I guess), and in most instances, it went down okay. The people who had issues with it, ironically, turned out to be among those for whom my respect has grown, rather than suffered. There are a few who I still call "prof" whom I really feel deserve the title, but those who prefered first names in general, and went for less formal relationships, have turned out to be the most inspiring and influential mentors. And then there were those who I never felt even vaguely at ease with. I have learned the hard way to follow my instincts on those ones.
Earlier this year, one of my undergraduate students called me "professor". I corrected her, explaining that I didn't have a PhD yet, let alone a professorship, and inviting her to call me Nicol. She switched to "Miss Hammond". That was more accurate, but, in light of my discomfort with professional identities and surnames, I wasn't nutty about it. When I tried again, the resultant "aunty Nicol" what a little terrifying! but very amusing. In South Africa, a sign of respect is to call an older woman "tannie" or "aunty". I get the respect thing, and am happy to practice it myself, but I feel so old when someone, expecially a student only a few years younger than me, practices it on me.
On the other hand, when I'm supervising my teaching students and am called into the principal's office to give my age, rank and serial number (or the academic equivalent), I almost wish I looked like an aunty....