Google killer-robots.txt
google.com
google.com
My favorite, by far is: http://www.google.com/#q=recursion
Edit: found the original interview:
http://www.npr.org/2003/10/14/167643282/google-founders-larr...
Starting at 13:45, Sergey and Larry try to explain recursion and idempotentence on Fresh Air.
Great example of whitelists vs blacklists. :)
Disallow: tells the robot that it should not visit those particular pages on a site. Or in this case, terminate those individuals.