Courtesy of Dr. Susan Lindquist, member of the National Academy of Sciences, from her talk Yes We Can! A Woman’s Perspective on a Life in Science, available as a pdf. 

A peasant girl, leading a donkey ridden by her grandmother, passes a group whose whispers are audible:
"How horrible! That perfectly healhy woman is making that poor child walk while she rides!" After deliberation, the grandmother dismounts and the girl rides. They pass another group who whisper "How shocking! That healthy young girl makes her old grandmother walk!" Both the girl and the woman mount the donkey. The next group remarks "Oh, look at those two people overloading that poor little donkey! After long deliberation, they dismount and carry the donkey. However, as they cross a suspension bridge, they lose their grip on the donkey, who falls into the chasm. 

Moral:
 If you try to please everyone, you'll lose your ass.