I've written about "Names, Power, and Intimacy" before, and the topic has come to mind again as I've been linking recently to the work of fellow bloggers and other types of writers.
When responding to my post about detecting uranium, Clayton Cramer called me "Mr. Williams". It was mildly discordant to me, because I don't really think of myself as "Mr. Williams"; it's a very formal style of address amongst peers these days, but still comes across as quite classy.
I often refer to Eugene, Glenn, SDB, Bill, Donald, and many other bloggers by their first names, and I have wondered if that's impolite considering that I don't really know them other than through the internet and their writings. When writing, I'll generally establish a person's identity by using their full name and a link, and from that point forward I'll use their first name. I realize it's overly familar, but the option of "Mr."-ing and "Ms."-ing everyone feels far too aloof.
So, as far as my blog-protocol goes, I've decided to operate as I would in "real life". If I have exchanged emails with someone or otherwise interacted with them other than through blog posts, I will generally refer to them by their first name, just as if we had met at a social function. Otherwise, I will use their full name and -- if required by the structure of my post -- their appropriate title and last name.
This is not to say that I find this arrangement ideal; I do not. As I wrote in the above-linked essay, I think it would be quite enjoyable and proper to return to more formal modes of address. Nevertheless, it feels awkward to do so myself, and I generally choose not to. Perhaps this feeling of awkwardness is the result of my informal blogging style; if I were writing an acedemic paper or a newspaper article I would certaily revert to the formal mode.