The Oxford comma did not actually originate at Oxford University in England. One can trace its origin in English guides from the early 20th century. The Oxford comma is "correct" in American Standard English but does not exist in other languages, nor is it mandatory in British or International English.

Sometimes leaving out an Oxford comma can lead to bigger issues. A simple syntax error in a dairy truck driving description was the start for a ten million dollar lawsuit.

The union contract stated overtime pay would not be given for “the canning, processing, preserving, freezing, drying, marketing, storing, and packing for shipment or distribution of agriculture produce.” The ambiguity of the "or" in relation to packing for shipment or distribution of agriculture produce had some drivers wondering if those distributing but not packaging were legally eligible for overtime. Adding a comma after "shipment" would have clarified the meaning. 

To avoid this issue, the Legislative Drafting Manual warns lawyers and legislators that commas in general are “the most misused and misunderstood punctuation marks in legal drafting, and, perhaps, the English language."