But, in many cases, yes. If you are an employee of the State of Oregon, your salary to the penny is a public record and accessible online. Of course, your salary may not be your only source of income.
Many companies, especially unionized shops, have fairly narrow salary ranges for specific jobs and titles. If you are a Press Operator Grade 3, then you make between $X and $Y where the difference between X and Y may be only a couple of thousand dollars per year. Of course, those salary brackets are published and so, if you know someone's job title, which is also usually published, you can know their salary within a couple of thousand dollar per year. Again, your salary may not be to totality of your income.
My feeling is that the information is well within the realm of personal and private information. What you and your employer have agreed has nothing to do with anyone else (other than tax man). Companies have their levels and most often your level is not disclosed or the benefits and extras kept qt. There are exclusions where your consent is implied on joining.
I have no great problems about others knowing what I earn but rarely disclose it. Obama is nuts to want to allow everyone's income become public domain. Spam and marketing compasses would swing due$ with con artists locking and loading. (they would probably not be that interested in Govt employees). Banks already have copies of your payslips from your loans.
What good would it do? Do my friends, colleagues and postman need to know?
Many employers forbid their employees to discuss their pay rate with other employees. These companies also tend to be the ones that get sued when it's discovered that female employees make a fraction of their male counterparts doing the same job.