As much as I like the Oxford comma, I don’t usually insist on people using it. For me, what’s important is consistency rather than a specific rule. However, there are cases where one choice can lead to disaster.
For example, a company in the US could lose millions of dollars in overtime pay because of a single comma.
Note the lack of Oxford comma — also known as the serial comma — in the following state law, which says overtime rules do not apply to:
The canning, processing, preserving, freezing, drying, marketing, storing, packing for shipment or distribution of:
(1) Agricultural produce;
(2) Meat and fish products; and
(3) Perishable foods.
Does the law intend to exempt the distribution of the three categories that follow, or does it mean to exempt packing for the shipping or distribution of them?
This just shows the havoc that can be brought about by syntactic ambiguity.
On a lighter note, there’s this funny graphic that shows you why the Oxford comma is important.