How many letters today start with Dear Sir or Madam?

well, at least letters that I write, I am afraid. the question how to start a letter if you know that there will be a person (a secretary, an officer, a scientist) who will open it but you don't know his/her name. we were taught this "Dear Sir/Madam" formula, which I know is awfully formal but would "to whom it may concern" be better?