Forum Moderators: open
Google's content removal help page [google.com] outlines the method for urgent removal.
Note that there are other robots designed specifically to disobey /robots.txt, so anything of a sensitive nature cannot be protected in this manner.
You can exclude all well-behaved robots, some well-behaved robots, or no robots - whatever you like. Take a look at Brett's robots.txt tutorial [searchengineworld.com]. I use the term "well-behaved" because, as ciml noted, some "bad" robots are designed to ignore robots.txt.
Jim