I guess I was raised in that "different time." When I was about four, I got scolded by my foster-mother for addressing my seventy-five year old neighbor as "Tony." Never mind I was just repeating what I'd been hearing from others, included my playmate.
But I think it's also about respect...regardless of which form of address. You can address someone as Mrs. or Mr. So-and-So and say it in such a way that it's snide. Or you can address them by their first name with sincere respect.
Now, there are certain people I cannot imagine addressing by first names unless they told me to...if, for example, I met Julie Andrews or Stephen Sondheim, I couldn't see calling saying "Nice to meet you, Julie" or "Hi Stephen."
But, at stage doors, it's always been casual enough that I've never addressed people too formally. I can't imagine saying, "Mr. Jacoby" or "Mr. Cerveris" at "Sweeney Todd." When I went, it was Mark and Michael. Informal, but still with respect.
The first time I talked to Hugh Panaro, my friend and I quite timidly addressed him as "Mr. Panaro." Before we finished the sentence, he'd stopped us with, "No, I'm just Hugh."
I think it's something that just varies from person to person.
As for people referring to the actors by the character's names...that bugs me, too. Especially since the people doing it usually have the Playbill right in hand to be signed. Would it be so hard to peek inside and check for their names?
Though my favorite was at the Majestic...I was leaving through the alley and a woman with a kid came up to me. I figured she was going to ask me if "the Phantom" was coming out to sign. Instead, she asked me, "Is Mr. Crawford coming out to sign autographs?" Forget checking the Playbill, someone needs to check a calendar.
http://www.hugh-panaro.net