Vampire Weekend has it all wrong.
The Oxford Comma (also called the Serial Comma) is indeed important – and it’s useful for writing clearly and directly, which is more than can be said for the hipster band’s song about this piece of punctuation.
There are two ways to list various items in a sequence. One is to list them by separating all but the last two items with commas, like so: apples, oranges and bananas. The other, known as the Oxford comma, is inserted between the last two items in a sequence. For example: apples, oranges, and bananas. It’s considered to be optional by most writers, and AP style – used by journalists in the US – actually discourages its use. The Oxford comma is also less popular in the UK, Australia, and other parts of the world than it is in the United States.
So why use the Oxford comma?
First of all, it makes sentences a lot less ambiguous. There are a lot of funny examples of sentences derailed by a missing Oxford comma, but this is a good one:
Second, it’s also helpful for consistency’s sake. Because commas are frequently used to introduce concepts, address listeners, and set off descriptions, they can become confusing if they’re used the same way for different reasons. That’s where the Oxford comma comes in. It doesn’t remove all ambiguity from a sentence, but it does make the difference between an introduction and a list of items clear.
American journalists tend not to use the Oxford comma for spacing reasons. They claim it adds unnecessary bulk to the written sentence and that it’s made redundant by the use of “and” and “or”. However, I think it’s a helpful little mark that doesn’t use up too much space. When given the choice between clarity and an imperceptibly shorter sentence, I’ll take clarity every time.