The local post office in Westborough has a far-too-lax postmaster. For the 5 years I've worked in that town, at the same office building, the letter carrier has arrived wearing whatever he wants. No hint of a uniform or other professional attire. He (and it's always been a guy that I've seen) arrives in a Post Office truck, carrying a tub of mail which he puts in our reception area or our cubby in the building's mailbox matrix. He collects the mail from the communal mailbox and drives away. All pretty ordinary, except that there is nothing on him to identify him as a postal employee. He could be any schlub off the street, or (for the paranoid) a terrorist, placing bombs and stealing checks and stuff. It is just unprofessional and a lousy reflection on the Postal Service in particular and the US government in general. (And God knows we don't need any more of that!)
I know that it's a poor (and unproductive) practice to complain about something if it's not to someone who can actually do something about it. So I might just copy and refine this rant and mail (!) it to the local Postmaster.