I think people need to mellow out on complaints about the lack of use of the "serial" or "Oxford" comma. The way English textbooks handled this matter has changed in my lifetime. While the Oxford comma is now standard usage in American textbooks, it wasn't for people educated more than forty years ago. Textbooks in England still call for its omission (and after-all, the language is still called English).
In addition, several style guides still call for its omission, including the style guides of "The New York Times", "The Economist" and the Associated Press. It is also never used in a company name, as in "The Law Firm of Dewey, Cheatem and Howe."
The only time to get upset, is if your office/organization has adopted a style guide (their own or someone else's), if the use/non-use is inconsistent within the same writing (as in this post, where I have used it, except in the paragraph about style guides that call for omitting it), or if the use or non-use of the Oxford comma creates an ambiguity. The following paragraph provides examples, taken from the Wikipedia Article on serial commas, where each usage creates ambiguity.
The lack of an Oxford comma creates an ambiguity in the following dedication: "To my parents, Ayn Rand and God." It is unclear whether this is a dedication to four entities (mother[1], father[2], Ayn Rand[3], and God[4]) or a dedication to two people (a mother[1] and a father[2], who are Ayn Rand and God). Likewise, the usage of the Oxford comma creates ambiguity in the dedication "To my mother, Ayn Rand, and God." Here, it is unclear whether the dedication is to three entities (my mother[1], Ayn Rand[2], and God[3]) or to two (my mother[1], who is Ayn Rand; and God[2]).
Sometimes, a phrase can be ambiguous whether or not the Oxford comma is used. In those cases, you should re-write the sentence with a few more words, and break down and learn how to use a semicolon (see the last parenthetical of the previous paragraph). The Wikipedia Article procides the following humorous example:
The Times once published an unintentionally humorous description of a Peter Ustinov documentary, noting that "highlights of his global tour include encounters with Nelson Mandela, an 800-year-old demigod and a sex toy collector". This would still be ambiguous if a serial comma were added, as Mandela could then still be mistaken for a demigod, although he would be precluded from also being a sex toy collector. The Wikipedia Article used a more specific word for "sex toy", which Woot's word filter would have altered with the result ruining both the meaning and the humor.
