I have two whiteboards and a chalkboard at home; I never code on such contraptions. (I like to draw pictures for programmers, but using Balsamiq or something.)
Now, obviously if I were in a situation where showing off whiteboard-coding were useful to me, I'd practice until fluent. But it's so bizarre, this fetishization of whiteboard technology.
Maybe it's good to communicate using pictures, rather than symbols. But if that were the real reason for whiteboard interviews, interviewers would speak of pictures; not whiteboards, nor syntax. Or one can argue that companies like rely on whiteboard tech to communicate; but then why not ask prospective workers to practice it as they would vi or emacs? Or spread the gospel somehow? Is this some weird entrance test, to see if a candidate proactively adapts to this weird obstacle?
As an interviewer, I'd feel I've ironically failed a meta-test, if I didn't accomodate a significant number of people's feelings on this matter. I would therefore not be fit to judge anyone's ability to think effectively.