Just a quick anecdote: I worked for a public university while I did my MPA. It was common knowledge that a book in the library had EVERYONE'S salary in it. All I had to do was go downstairs to find out how my supervisors and co-workers made. As this was my first experience in the workforce, I didn't realize that this wasn't the norm. I got in BIG trouble at my next job when I emailed someone in my Finance Dept with a question about my paycheck and referred to the amount.
I personally don't really care if people know how much I make. If all nonprofit salaries were public information perhaps we'd see greater wage equity by gender, and nonprofits would start being more competitive in their salaries...
Anyways, that's just my slightly irrelevant 2 cents...