He went to the grocery store, the bank, and the mall.The Oxford comma is a stylistic choice, but it is one that I am fond of because it helps eliminate ambiguity. For example:
In this screenshot, the information from Sky News lacks the Oxford comma, and ends up being guilty of amphiboly by making it sound as if Obama and Castro have set the date for their same-sex marriage. Without the comma the sentence is ambiguous and can be interpreted in several ways. With the inclusion of an Oxford comma the sentence would read as follows:
Top Stories: World leaders at Mandela tribute, Obama-Castro handshake, and same-sex marriage date set...With the inclusion of the Oxford comma it becomes clear that these are three, distinct news stories, not two stories, one about the Mandela tribute and one about the Obama-Castro relationship. Because it helps avoid these kinds of ambiguity, I am a fan of the Oxford comma.
h/t to George Takei