I am amazed that in all these posts, hardly anyone mentioned cell phones and their misuse; which can range from talking on one while in a theatre to something like ignoring a check out clerk because you just must get this call. Cell phones are great things, but have turned a lot of otherwise decent people into jerks.
Bingo! The newest manifestation of this rudeness is use of those new push-to-talk phones. You know, the ones that emit a loud "chirp" and then you not only hear the idiot who is in the store/theatre/restaurant, but you also get to hear the *other* person thanks to the loudspeaker. This has got to be the worst of the worst.