Serial Comma Killer and Culling the Herd

Yesterday I was introduced to a punctuation controversy I had never encountered before--the serial comma.  Consider the following sentence, if you will.

"Mary, Peter and Josh went to the store to buy some bread."

This is how I would write that sentence.

"Mary, Peter, and Josh went to the store to buy some bread."

Basically, a serial comma is a comma that immediately follows the penultimate item in a series.  According to my English teacher, it is not good grammar to use them.  This prompted me to do a little Wikipedia reading and credible source follow-up.  It is conventional to use serial commas in everyday writing (which explains why I use them impulsively), but they are less common in British English and in journalism.  We just had a writing test at school with a possibility of an editorial or article format, so that is probably why my teacher brought it up; nevertheless, I like serial commas.  I remember eating out at a restaurant once and looking at a menu that read, under the specialty sodas heading, "grape, cherry, orange and cream".  Since menus sometimes leave out conjunctions altogether, I didn't know if it meant there were orange sodas and cream sodas, or if there was a particular soda that was both creamy and orange-y.  In a final testament to the ambiguity that abounds when serial commas go missing, there's somewhat of an urban legend of a writer who dedicated her book "to my parents, Ayn Rand and God."

In other news, apparently my school library has to throw out a ton of books that don't have recent enough copyright dates, yet some of them are classic fiction books that have been out of print for ages!  This is absurd!  I rescued a box full of them today and will probably go back for more, but too many books will still tragically go to waste.  At least I got my own copy of Heart of Darkness out of it.