Completely unproven, but all I see this doing, is driving down wages. No one will say "I think we are not paying enough, looking at this average". It will be "We are paying far too much, lets bring ourselves inline".
So these kinds of reports are useful for supporting our answers to questions like "Why do you say none of the applicants for this developer position are qualified" when we answer "because you'll only offer $50k/year".
Now as for whether that will actually play out and result in salary increases remains to be seen.
I find most companies are generally in the know on how well they're paying their employees (employee retention, counter-offers, etc), it's the employees that lack this information.
But they have to be fairly on the ball, and many people just aren't.