Where did newspaper editors get the idea that this rule makes any sense? I hate this notion. Hate it, hate it, hate it. The serial comma should be used consistently, because grammar is, after all, supposed to help you express yourself clearly -- not undermine your meaning.
If you're not consistent about using the serial comma, then you wind up with goofs like the pious author who dedicated his book to "My parents, the Pope and Mother Teresa." Ooopsie!
An article in this week's Time magazine made me do a similar doubletake just now. It notes that Dallas, Texas is fast becoming quite the gay-friendly city (yes, that Dallas, Texas):
Both the Dallas sheriff and the county judge--an Old West title meaning chairman of the county commissioners--are openly gay. The district clerk is gay too, and Dallas is home to what is said to be the largest gay church in the world, the Cathedral of Hope, which has 3,500 members, a full choir, a violinist and long-stemmed roses in the bathroom.Now tell me, are parishoners serenaded or not when they pee? How do we know for sure? If we all used the serial comma consistently, there'd be no doubt. Feh.
Update: Note that in the comments section below, a staffer assures that the Cathedral of Hope most certainly does not have a fiddler on the loo.