Whom to help first?

Imagine, at the reference desk, you receive reference questions from the following individuals at the following locations through the following "channels," all within ten minutes of each other:

1) An e-mail reference question from a student studying abroad in Germany.
2) A walk-up patron who traveled 20 miles to use the library's collections.
3) A telephone call from a faculty member at home.
4) An instant message (virtual reference) from an administrator in his or her office.

There is some debate about whom to serve first and why. Many people would be inclined to say, "Help the walk-up patron first. After all, she/he made the effort to visit the library, so he/she deserves to be served first."

However, I have to agree with the LibrarianInBlack and others, that "synchronous" reference questions should be handled in a first-come, first-serve fashion. ("Synchronous" meaning a "live" or "real-time.") Thus, if I am helping a patron via chat (instant messaging or some other virtual reference mechanism), I should finish helping that patron if another walks up during the reference interview. Or, if the phone rings at that time instead, I would answer the phone, explain that I am helping another patron at the moment, and could I please call back just as soon as I am done? Asynchronous questions (in this case, e-mail), can be answered when time permits (but, of course, in a timely fashion).

I think our profession's Code of Ethics provides guidance on this issue. We can't discriminate patrons based on their preferred mode of communication; librarians must provide "equitable" service. And, as one reader of the LibrarianInBlack notes, some of those people who can't make it to the library might not be there for a good reason. For example, a person calling from home might be disabled.