I work in municipal government, and I always refer to our residents/customers/visitors as “Mr./Ms. LastName”, until/unless they tell me to call them something else. When speaking to them about my bosses or coworkers, I use last names as well - for instance, “Mr. Smith, Mayor Jones is in a meeting, but perhaps our Clerk, Mrs. Davis, can help you?” I just feel it is more respectful to be a little formal in a business situation.
Except for teachers, my kids refer to most adults who know them well but are not related to them as “Miss/Mr. FirstName”, to show respect for them; and the other parents in my neighborhood have picked this up and their kids now do the same.
Drives me nuts when strangers call me by my first name without asking my permission. My doctor’s office used to do this, so I started referring to the doctors by their first names; the receptionist seemed to be appalled by this, until I explained that, since we were obviously on a first-name basis, it must be appropriate. Since then, they call me Ms. Comedienne (and probably call me other things behind my back).
I used to appear in front of one judge that would sometimes refer to me as “The Learned Public Defender,” when sustaining an objection. “The Learned Public Defender has a point.”
He was just strange. Kind, courtly, even, but strange.
It can get a little weird, I’ll admit. I tend to call my clients by their first name, and I talk to the other lawyer (using his or her first name) about their client, using his or her first name. But in court, it’s more formal address; and as Northern Piper notes, here in Canada, the other lawyer is “my friend” in court.
The same applies to letters, now that I think of it. I can call the lawyer representing the other side, and use his or her first name (and we’ll talk about our clients by their first names during our call); but when I confirm the phone call in writing, it’s “Dear Mr. Smith,” and “Ms. Brown’s offer,” and so on.
Interesting sidenote: I once had a client who was a veterinarian. As you might guess, he was, to me, “Bill.” [All names in this anecdote are fictional.] In all written correspondence, both to my client and the other side, I referred to him as “Dr. Smith,” which was his preference. But written correspondence from the other side always called him, “Mr. Smith.” In phone calls, and among other topics, I repeatedly told the other side that my client preferred to be called “Dr.” but it didn’t seem to stick. So when we got in front of a judge, and the other side called him, “Mr.” more than once; we had an interesting time when I asked the judge to remind the other side that my client had earned his DVM, and therefore, the right to be addressed as “Dr.” The judge did, and from then on, to all parties, my client was “Dr. Smith.”