Some of my Facebook friends recently pointed out a Facebook group entitled:
"'Let's eat Grandma!' or 'Let's eat, Grandma!' Punctuation saves lives!"
The page contains amusing examples of mangled English and unintended messages, as well as discussions on usage. One discussion is on the Oxford comma.
An Oxford comma is the comma before the conjunction in a series. In the following sentence, the Oxford comma is immediately after the word "barbecue":
He bought corn-dogs, barbecue, and cotton candy at the fair.
Newspapers that use the Associated Press Stylebook eliminate the Oxford comma, deeming it unnecessary. The purpose is conserving space — all those commas add up, you know.
But leaving it out can have unintended consequences. An example from the Facebook discussion, sourced to a Peter Ustinov documentary:
"Highlights of his global tour include encounters with Nelson Mandela, an 800-year-old demigod and a dildo collector."
Either that describes a most eclectic tour or it reveals things I never would have suspected about Nelson Mandela.