Google's motto is "Don't Be Evil" — but they sure have an evil non-disclosure agreement! In order to be considered for employment there, you must sign an agreement that forbids you to 'mention or imply the name of Google' in public ever again. Further, you can't tell anyone you interviewed there, or what they offered you, and you possibly sign away your rights to reverse-engineer any of Google's code, ever. And this NDA never expires. Luckily, someone has posted excerpts from the NDA before he signed it and had to say silent forever.

http://cscott.net/
http://valleywag.com/tech/google/this-nda-never-existed-230407.php