From the brochure “Playing It Safe on the W&OD Trail”:

“Always look ahead for obstacles such as gates, potholes and other trail users, etc.”

You didn’t know that potholes were considered trail users? Reluctance to place a comma before the “and” in a list of three or more items often results in ludicrous statements such as this.

More seriously, such (mis-)usage often results in ambiguity, confusion, and loss of meaning.

Consider how professional speakers (such as TV and radio news reporters) almost always pause before the “and” in these cases; they are mentally inserting the comma, exactly where it should be.

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