Internet (and by extension, LJ) pet peeve #539478:
Failure to list event location. People seem to forget that the internet is not localized, but non-digital events are. People regularly post that some fun event is happening and give a club/bar name or a street address, but rarely include the city/state/nation/planet the event is occurring on. Would it be so hard to include, at a minimum, the city and state of the event?