This tweet has been making the rounds as an illustration of why the Oxford (serial) comma is necessary, including a few gloating notes from friends (because those are the kinds of friends I have):
But, while Stephen Harper isn’t in my top 5—or 5000—politicians, this example doesn’t mean what my friends think it means. Adding a comma just creates a different ambiguity. Who in the “fixed” sentence, “Special mention to @LaureenHarper, my mother, and daughter,” is Laureen? Harper’s mother or someone else?
As with many such examples here, the problem isn’t a missing serial comma (for the record, I am 100% pro-Oxford comma where needed to prevent ambiguity), but a sentence that needs to be rewritten.