I think salaries should be required-- if not by rule, then by convention.

Companies have been asking candidates to give their salary up front ("expectations" or "history") without ever justifying it when it's obviously not in our best interest to do so...yet they do already have a budget for these positions, so let us decide if we are in the range or not. (Rather than applying for jobs which will never offer a salary commensurate with our experience because we read the demand for high end skills and "salary commensurate with experience"-- and don't realize it's someone trying to score a deal, and not really offering a market salary.)