I can't stand it when people are late. If you know me at all and have spent anytime with me while we are waiting for someone, you know that tardiness makes me go crazy. Out of all rude behaviors, this one lack of manners is the worst.
I know people who are late don't really think about the people that are waiting, but what blows me away is that most people that are late DON'T EVEN APOLOGIZE! Some even come in acting annoyed that the people who are waiting are annoyed. I don't get that.
It is my opinion that when people are late, it means that their time is more valuable than mine. I know this a 'chip on my shoulder' view, but it's my pet peeve.