Copied from a reply I made to Luke727 which brought back some memories:
Back early in my career, I worked for the first ISP in the UK (UKOnline), and myself and a good friend were charged with coming up with the 'first password' routine for the service.
Now Joe being Joe, decided the best way would be to use a dictionary, and then provide, if you will, an anti-dictionary - a dictionary full of swear words.
We would take two words based on this algorithm, and separate them with a dot.
Joe sent an email around the offices asking everyone to send back an email with all the swear words they knew, so that we could use it as the anti-dictionary, and filter the real dictionary based on it.
You wouldn't believe some of the mails that Joe received - some really dirty ones from people you wouldn't expect, either.
Anyways, the system was setup and sure enough, if a word was found in the dirty dictionary, it wasn't used as one of the pieces of the password.
Sure enough, three weeks after going live, customer support received a really annoyed and offended call from a female customer who had received:
I shit you not.