I think of the CS department here as pretty informal — and maybe it's part of a general trend in academia, I don't know — as we refer to all the faculty pretty much by their first names to their face, and otherwise. We don't have Dr. Pfenning and Harper and Crary, we have, you know, Frank 'n Bob 'n Karl. Then again to me Reynolds is Reynolds to me, and professors in other departments are fair game for, you know, respectful titles and such. But! There is an entirely separate and quite healthy T-V sort of distinction in the ability of people to refer to eachother by andrew ids or other such nicknames. Apparently the faculty still find this practice very weird, approaching linguistically abhorrent.