Thomas Kistler, President of Pennsylvania's 49th Judicial District, has put out a warning to all those who like to play fast and loose with the rules of English grammar:
Kistler has a funny understanding of the word "friendly." You'd think that an Oxford friendly facility would simply accept the Oxford comma as a valid choice, but not the only valid choice. Instead, Kistler has declared that those failing to use it will be looked down on. That's not Oxford friendly, that's Oxford supremacist. Not cool, Judge. We hope your court isn't also a "family friendly" facility.
Okay we know he's just kidding around. He's wrong though.
There are times when the Oxford comma is certainly needed, but there are plenty of times you can go without it. In the judge's own declaration it's not necessary. In situations where the Oxford comma is needed to resolve ambiguity, definitely use it. In situations where it doesn't add anything, take it or leave it according to your own personal tastes.
Now, you might be thinking that if sometimes you do need it, and there's never a time where it's wrong, why not just always use it? There are two reasons.
First, by unthinkingly using the Oxford comma every time you pay less attention to your writing. Making conscious decisions about its use forces you to slow down and consider your sentence structure. Making a habit of thinking about your writing will improve it more than a habit of using Oxford commas.
Second, there can be consequences to liberal comma usage: