It is absolutely true that, like marketing, public relations should be proactively focused on setting goals and objectives that are in sync with the organization's overall mission and goals. As always, these should be SMART goals (specific, measurable, attainable, relevant and time-based).
In days past it was not typically considered important to directly measure PR efforts, largely because most business executives had no idea how to do so.
How specifically do you think the value of the PR function should be measured within an organization?