Ethical consideration: Who should be allowed to “know”?

Consider that you work in the human resources management department of a local business and that many of your friends work there.  Although you don’t personally generate payroll checks, you still have the ability to look up anyone’s salary.  Would you check on your friends’ records to see if they’re earning more money than you?  For that matter, would you look up their salary just out of simple curiosity, knowing that you would never do anything with the information or share it with anyone else?  Why or why not?  People working at the Internal Revenue Service (IRS) were caught just curiously looking up the reported incomes of movie stars and other high-profile public figures.  Is this acceptable?  Why or why not?