Sadly, there are people who have email accounts, but only a limited grasp of basic computer or social skills. Matthew Inman of The Oatmeal has a new set of comics up illustrating the foibles of such folks.
Link
What email habit do you find most irritating?
an email about how special i am that they want me to send back to them. WHY?!? oh, and they also sent it to 20 other people.
Sigh.
I replied and explained what a BCC was. The office staff probably hates me now.