They should thank Gregory for raising the level of debate about how practitioners can measure their return on investment and for at least trying to create solutions on how such mechanisms might work. But by collectively appreciating the ROI lobby's endeavour, the industry earns the right to question aspects of its approach, and there are two specific points worth raising.
First, critics of PR's introspection would - and, at The Communication Directors' Forum last week, did - point out the imbalance between the effort directed towards delivering value and that which is directed to demonstrating it. This is logical, since the more time one spends boasting that one is doing a good job, the less good a job one has time to do.
In response, Gregory - and her co-presenter Dora McCabe, Cadbury Schweppes group media chief - said that striving to prove ROI need only be temporary.
Once management was aware of the value PR can deliver, there would be no need to re-prove the point, and more time to spend on the day job.
But the second, more important problem arises in the process of what Gregory calls 'disaggregation' - that is, trying to disentangle the contribution PR made to a campaign and comparing that to the value created by, say, advertising. Unless PR operated in isolation, this is nigh-on impossible, and attempts to achieve it range from meaningless guesswork to self-interested puff.
The whole thrust of marketing communications over the last decade has been a process of integration, with discipline-neutral briefs and all skills deployed seamlessly. We are now told that, while this is still vital at the planning and execution stages, it needs to be complicatedly unpicked in evaluation. That can't be right.