In the meantime, I suppose individuals can approximate the same behavior by writing such things in a file on their hard drive. It won't affect processing of the survey, of course, but then it wouldn't really do so anyway.

Longer-term, presumably the goals we want to achieve with a question should drive the options we provide for answers. If we want to correlate demographic category with other answers, then we really don't care about demographic categories that cover fewer than 5% or so of the population, since such correlations would be even less useful than baseline, but we do care about standardizing answers. If we want to know how LessWrong readers identify themselves because we're curious, we don't really care about standardizing answers, but we do want to let respondents use their own terms to describe themselves. Etc.