Usage varies on the matter of the “serial comma,” the comma between the last two items in a series. Newspapers routinely omit it, and book editors just as routinely put it in. Does this mean that the comma is merely a matter of taste? Usage experts don’t think so.
Yes, newspapers ask journalists to omit the comma to save space—or even ink—and journalists wisely comply. Even so, most experts agree that the practice itself may not be so wise, because omitting the comma can result in ambiguity or misreading. Wilson Follett gives an example of ambiguity:

How many items are in the series—three or four? We can’t be sure. In fact, the writer meant to list four items, says Follett, and the comma would have made this clear (399).
Omitting the comma can also cause misreading, as in this next example, also from Follett:

Three Presidential “imperatives” for the year were defense reorganization, extension of reciprocal trade and foreign aid.

Follett explains the problem and its solution: “You first read reciprocal trade and foreign aid as co-ordinate objects governed by extension of, and you are still waiting for the third member with voice suspended. A comma after trade would identify the third member for what it is” (400).
Conclusion: If you are writing for a publisher who asks that you omit the comma, by all means do so. Otherwise, use that comma—it is worth both the space and the ink.