I don't care either way what I'm called, but DS calls:
My two closest friends "Auntie April" and "Auntie Joanna".
My circle of younger (i.e. my age, in their 20's)friends by their first names, John, Monica, Jessica, etc.
All older men he refers to as Mr. Surname
Most older women he refers to as Mrs Surname, though a few who are well known to us (shopkeepers in a small towm) he calls Ms Kay and Ms Joan. (That's a southern US thing, Mzzzz Firstname :), and I've always liked it though we don't live in the south)
His teacher is Miss Firstname.
He doesn't have a lot of outside friends yet (I mean friends who aren't children of my friends since he's just three) so he mostly calls them "Joe's/Lexi's/Sophie's mommy"
I don't know, I've just always liked him to call older adults by a title. Our neighbor told me that having DS call her "Mrs. Miller" when he sees her makes her happy. :)