So, this disillusioned and pissed off media exec pays several thousand dollars to have thousands of blank speech bubbles printed and stuck all over NY on his own advertisements... then just waits for members of the public to fill in the blank spaces. One of my favourites:

http://www.thebubbleproject.com/01.Bubbles/StreetBubbles/03Politics%20and%20Religion/03Politics.htm

Bloody brilliant.