Anyway, a good expansion on “language change is not decay” is the exploration of “register.” For instance, no one writes academic essays the way they talk to their friends, family, or even colleagues (unless you’re giving a talk – then it’s questionable).

In fact, those three groups I just mentioned also elicit three other, different registers. You might not say “Dude! That was sick!” to your family or colleagues, and I doubt you’d say, “Aw, c’mon, Professor. I d’wanna go ta class today.” And while you might try to use technical jargon with your friends (especially if they’re in the same field as you), it’s generally considered poor form to be sesquipedalian in bars or at parties.

For more on the use of register, and switching between registers, see William Labov’s work on language change, sociolinguistics and *especially* his NYC “Fourth Floor” study (briefly summarized here: http://www.ic.arizona.edu/~anth383/unit4.html ).

I love to eat spinach, peanut butter and tuna.

vs.

I love to eat spinach, peanut butter, and tuna.

Without the Oxford comma it sounds to me like you would be eating them together like peanut butter and jelly, which is gross.

At the beginning of your post I feared your disdain of commas, since I adore them. I love that they can clarify clauses, or can be used to indicate breath. To me, good writing has a rhythm to it and commas help indicate beats. However, since you respect the Oxford comma, I can let it go.

Vampire Weekend actually has a song called Oxford Comma… unfortunately it is less than flattering toward it.