The Topeka Capital Journal has this on the Postal Service's denial of revenue figures on a Kansas post office which it limited the hours of recently. According to the Postal Service, they were denying the revenue figures because they could be used by potential competitors. I'm not sure who is planning on opening another postal service soon, so I'm not sure who these competitors are (UPS and Fedex may be in the shipping business but they do not mail letters for less than fifty cents, I wouldn't call them full blown competition and am not sure how they could use this information in any event) -- maybe the Chinese will extend their postal service to America?
This isn't the way transparency is supposed to work and is probably much of the reason that the Postal Service loses lots of money each year (my local post office has some of the most bizarre business practices I've ever seen). Local citizen input on a local post office would go a long way to helping the Postal Service, not hurting it.