Mike Nichols, the director of The Graduate, had a practice of leaving the camera running long after the scene ended just to see what the actors would do. The original ending of the movie was supposed to be after Ben and Elaine smile at each other, but Nichols liked how their expressions sank so much that he kept the long take thus changing the tone of the movie entirely. The found ending ranks among one of the all time best endings ever.
the Whole Garden Will Bow 
VERY interesting. But: Where do you know that from? I´d love to know!
Mike himself said it on the DVD commentary with Steven Soderbergh.
Thank you!