I was never taught about the Oxford Comma (I'm not a native speaker), but trained myself to use it consistently after seeing this http://jaced.com/blogpix/2013/washingtonlincolnoxford.jpg . This has made me rethink though - he makes a great point that writing is about transferring the voices in my head into the readers', so I'll keep that in mind for any creative writing. Heck, not just creative writing, I can think…
Consider though: To my mother, Ayn Rand, and God [1] Is the writer's mother Ayn Rand? [1] http://en.wikipedia.org/wiki/Oxford_comma#Creating_ambiguity
Remove the comma and their mother is both Ayn Rand and God. That's a really terrible example since the Oxford Comma actually works slightly better than the alternative since the problem there is the ambiguity created by the ordering, not the punctuation.