An intriguing read from the comma queen, Mary Norris, on serial comma:
The serial comma is the one before “and” in a series of three or more things. With the serial comma: My favorite cereals are Cheerios, Raisin Bran, and Shredded Wheat. Without the serial comma: I used to like Kix, Trix and Wheat Chex. Proponents of the serial comma say that it is preferable because it prevents ambiguity, and I’ll go along with that. Also, I’m lazy, and I find it easier to use the serial comma consistently rather than stop every time I come to a series and register whether or not the comma before the “and” preceding the last item is actually preventing ambiguity. But pressed to come up with an example of a series that was unambiguously ambiguous without the serial comma I couldn’t think of a good one.
I have been putting the comma back (before the “and”) in my writing. For many years, I don’t include the serial comma because it appears to be cleaner. Then again as Norris points out, “The bottom line is to choose one and be consistent and try not to make a moral issue out of it.”