I think this is an interesting thread. I personally don't care if folks call me by my first name or doctor, in fact I am most comfortable with my first name, but I had to react to that earlier post that only MDs deserved the title Dr. But, its also important to not overinterpret someone's reasons for correcting someone. For example, if someone wants to formally address me and calls me Mrs. L, I will correct them that it is Dr. L, not to be snooty, but because Mrs. L is my mother, not me. That is, I kept my maiden name, and Mrs. L implies that I am married to Mr. L which I am not, so either call me by my first name, or if you insist on formalisms, use the accurate formalism. Everyone who works for me in my lab, my grad. students, etc. call me by my first name, but med students call me Dr. L. since that is the covnention in the medical school courses (I run a research lab and teach medical students biochemistry). And I definitely correct people when they send an invitation to Dr. and Mrs. .........