There's an interesting discussion on Quora about the Oxford comma. Here's my favorite response (con Oxford):
1) "Who gives a Fuck about the Oxford Comma?"
That is a song, but it says things pretty accurately
2) It is a piece of punctuation. It does not have any intrinsic value: it is not content or art.
3) It is a piece of punctuation: it has usage purely through convention.
4) And in this case there are two, equally valid and equally widely adopted conventions.
This is much like arguing about whether to eat an egg from the big end or the little end (Jonathan Swift) or whether "colour" is better than "color"
America (in general) uses it; Britain and other English language in general do not (or, rather, only use it if the sentence would be ambiguous). Journalists in general do not (even American ones); academics (especially American ones), generally do. Amongst(**) British academics there is a slight Oxford (do) / Cambridge (do not) divide.
5) Deliberate sentences to show "look it is ambiguous" are a stupid exercise at the best of times. Anyone can write sentences that are ambiguous, and if you really want to do so then a piece of punctuation is not a panacea. The skill in writing is to communicate clearly and unambiguously: you can do that with or without Oxford Commas. If something is ambiguous, then use it. Otherwise, do not.
6) And along those lines for everyone who has wasted brain cycles on an ambiguous sentence that needs an Oxford Comma there is a counterpoint where adding that comma only adds ambiguity. As I said, a stupid exercise.
7) Personally, I follow The Economist Style Guide:
Do not put a comma before and at the end of a sequence of items unless one of the items includes another and.
Thus The doctor suggested an aspirin, half a grapefruit and a cup of broth.
But he ordered scrambled eggs, whisky and soda, and a selection from the trolley.
8) But The Times, The Guardian, Oxford University Style Guide (*), The New York Times and AP Style Guide all say the same thing:
The Times style manual: "Avoid the so-called Oxford comma; say "he ate bread, butter and jam" rather than "he ate bread, butter, and jam"."
The New York Times stylebook: "In general, do not use a comma before and or or in a series."
(*) As opposed to Oxford University Press which does insist on it and where the name comes from
(**) To use another thing with British / American division.