the economist does a story on pranks...

Abbie Hoffman, a 1960s radical-cum-trickster, said most pranks fell into one of three categories: “good” pranks were amusingly satirical, “bad” ones gratuitously vindictive, and “neutral” ones surreal and soft on the victim (if there was one). An example of the first is the time Mr Hoffman and his fellow “Yippies” showered the floor of the New York Stock Exchange with dollar bills in 1967, thereby managing to stop the tickertape for six minutes while traders scrambled to pick up the notes.