When I was a child, my mother told me a story. When she accepted one of her first jobs, her boss told her "Don't tell your salary to your co-workers, since they'll be jealous." After she eventually quit, she and her co-workers went to lunch and ended up exchanging salary information. It turned out that my mother had been the lowest paid employee. That's when she realized that the boss didn't want her to discuss salary so she wouldn't find out how poorly she was being paid.
So when I got a job offer and the department Chair said "Don't tell your salary offer to anyone in the department, since they'll be jealous," I burst out laughing.
From an early age, I've had a fondness for the adage "knowledge is power".