I've recently gained first-hand experience of this as I just found out a co-worker, who does the same work I do, is getting paid 30% more than me. Salary information is public here when it's above a certain level, and imagine my surprise when I had to look higher and higher up the pay scale to find my co-worker. They're getting paid more than managers and they don't manage anybody! It really sucks too because I voluntarily share information I come across, techniques I use, and I'm just helping them look better in my boss' eyes while it slows me down from getting my work done.

I've thought about asking for equivalent pay but small comments from my boss make me think it's probably best to move on. I'm not really in the job for money but I just think it's way unfair what I'm getting paid now. I can imagine the people who advocate keeping salary information private are the ones who benefit the most from the secrecy, and vice versa the ones who feel slighted want it public the most.