I guess I'll be the anecdotal evidence guy.
Five years ago, I started working with a remote team on a project. I was in Florida, they were in Seattle.
I was the one with the least amount of experience in the field, and my cost of living was undoubtedly lower, so I expected that I would be the lowest paid member of the team.
A year in, and I felt confident that my contriubtuons were no less vital than anyone else, so I just wanted to make sure things weren't too far off. So the next time I visited Seattle for work, I asked some co-workers out for lunch and asked about their compensation.
They were all pretty open and honest and altogether shocked when we worked out that they made 2.5x-3.5x my salary.
If I hadn't asked I wouldn't have had the leverage to ask for a pretty massive raise. I also wouldn't have had the information I needed to decide that moving cross-country would be better for me financially despite the cost of living increase.
I know people get weird about it, so I don't talk about it in general. But if anyone (family, friend, or a stranger at a conference)) ever asks, or even comes in the vicinity of bringing it up, I make it absolutely clear that I am willing to tell them what I make, as long as they ask me explicitly.