it's really bad in P2P programs too, I was searching for a song by the dead kennedys called "a child and his lawnmower" (a short and funny song about a guy shooting his lawnmower for not starting) and got a but load of links to downloads.
There's a disturbing trend hackers and other miscreants who put spyware on your computer to redirect you to kiddieporn sites, record your activities, then turn you in to the FBI for a reward.
It's frightening how easily someone, government or otherwise can watch, control, or mess up your computer.