Yes almost all do and many have it in the company rules and guidelines that it is not permitted. Also, just in general, it is considered uncouth to talk about your salary. What you make is between you and the company and nobody else's business. How would you feel if you found out that someone who did the same job as you was getting paid more than you? Would you want someone who was doing the same job as you, but wasn't as good, to know that they weren't making as much as you?
