I found it hysterically funny. My three year old niece was following directly behind her mother at the living room windows. For every pane of glass my sister cleaned, my niece rubbed her hands all over another—all in the spirit of "helping her momma." In seconds she had completely undone the window cleaning process.
Somehow, I missed that sense of humor when a gentleman followed directly behind me in the store rearranging the items on the shelf because I "didn't do it right." There was a small sense of cosmic justice though; he knocked over a candle jar which shattered on the floor. Apparently it wasn't as easy as he thought, so he left me to do my job. Thank you.