This poem, featured on Guy Kawasaki's blog, about how easily people can be replaced sounds amusing, but its message is both vile and inaccurate.
Positions can be refilled, but people cannot be replaced. You will find teams and organizations that suffer for years when one person leaves. To deny that is to deny the unique combination of talent and insight that some individuals bring to the job.
A reasonable case can be made that the Second World War would have been lost if Winston Churchill had not been prime minister of Great Britain. The other contender for the position, Lord Halifax, was far more inclined to seek an armistice with Nazi Germany; an act that would have significantly increased Hitler's ability to conquer the Soviet Union. Once in possession of the Soviet Union's resources, Nazi Germany would have had enormous power and the world would have been seriously altered.
Rather than touting poems about replaceable people, we should be emphasizing the importance of the individual.