Also rude, and also stupid, are telling a random person -- whom you may or may not know -- "You look tired," or my personal piss-off: "Smile."
A recent Ask Amy column reminded me of this crap. Here's why you need not announce what you think of someone's facade:
1. Any comment with any word with any possible negative connotation (fat, old, skinny, tired, frowny, etc.) is rude. You think your coworker looks tired? Keep it to yourself. What good can possibly come from such a comment?
2. You don't know -- nor should you -- what that person is going through at that moment. Maybe she just received some bad news, maybe she's distracted, maybe she's got the weight of the world on her mind. "Smile" or "You look _______" are not helpful or constructive; they're just asinine and rude.
Thinking of this reminds me of a truism my dad told me when I was in sixth grade, and he was talking about the very people I'm writing about: "When someone makes a stupid comment like that, it's because they're so empty-headed that they have nothing else to say."
I'm with ya, Dad.