Maybe where you work, most of my jobs you would get in a bit of trouble for talking about salaries... something this extreme at my job would most likely get you terminated :(

I work for a company where our hours are usually billed to customers. As your billing rate is tied to your salary everybody has a general idea how much you make. Very transparent and very honest system. If a customer is willing to pay your rate, your salary is fair. I just don't see why it's a big deal. The only reason I can think of is if the salaries are very unfair or there's a very big variation between different people doing the same job. All situations where it is not in the interest of most of the employeees to keep salaries a secret...

I wonder if they'll notice anything interesting when looking at salary / sales history, like evidence of the gender wage gap. Hopefully this is not still a problem for your company, but it generally is. If so, expect lawsuits for another reason (in addition to privacy matters).

a disparity in salaries doesn't mean that something odd is going on, but you can be sure that people will get upset about it anyway. If I start a new position where I earn, for ex. $35000 based on prior experience, and my coworker who has worked for the same company for longer than I have makes less than me, say $30k (owing to less experience, though he has more within the company), there is still the possibility of temper flareups and hysterical backtalking- justified or not. A disparity could also mean that someone got a higher raise than someone else, which also causes problems, since performance evaluations are not public information and someone may feel that another person's raised wasn't justified. Trust me, we have these problems at my workplace all the time. Salary and performance information should be strictly confidential. It's no one elses business and should remain between employer and employee. I'd be pissed if my salary and performance information were circulated in the office.