Here's one argument: the logic changes if the data is universal. The usual complaint about asking for salaries is that it's a trick to underpay new hires - you

Here's one argument: the logic changes if the data is universal. The usual complaint about asking for salaries is that it's a trick to underpay new hires - you can give them the lower of your normal salaries or a 10% raise. That's because they don't know what they're worth, but you know what they got before. If everyone publishes salaries (and they already do in practice, thanks to Glassdoor), that trick goes away. No matter what your previous salary was, you have leverage to say "look, you pay everyone else double that, cough up". So the primary objection to asking for salary is negated. I'm not sure the logic is totally sound - some people will end up moving from published to unpublished employers - but I think there is a distinction.