Going on a tangent here, if they also assume this stance - meaning, they'll tell you everyone else's salaries - it can be quite interesting.

I can't quite find where I first saw this, but googling a bit brings up a few interesting example. For instance, http://99u.com/articles/15527/the-age-of-salary-transparency

You say, tell me how much all your current employees make. Don't negotiate with someone who holds all the cards.

If you are playing to win, you tell them you currently make whatever salary you are seeking. When they ask you what sort of salary you need, say something along the lines of "Obviously, I want to take a step forward, but I am pretty flexible, so if you can at least match my current pay, then I would be open to accepting".

While this tactic does fall into the grey area of morality, it is quite effective.

    It would really hurt a company if their detail pricing
    scheme was released, as a competitor could easily
    undercut if they had access to that information

If every company's pricing were public, wouldn't we just have healthy competition?

Government contracts are usually public information already. More than once I've been at a company that sold something to a government agency, and the agency first had to publish what exactly they were buying and give someone else the ability to put in a better bid.