HOW TO: Crack Mac OS X passwords
As we are all aware, Mac OS X is based on BSD. Mac OS X is an UNIX-like operating system (much 
like Linux and the various other BSD variants FreeBSD, OpenBSD, NetBSD).
So what does that mean?
It means that your Mac is a multi user operating system. While at the present time, only one user can use your Mac at a time sitting in front of it, many users can login via an SSH session and use your Mac simultaneously. If one of those users has an easy-to guess password, the entire system can be vulnerable to being hacked.
Why would we want to crack Mac OS X passwords? Cracking the passwords on your Mac is a way to test the passwords to be sure they are not easily guessed or cracked. How to crack Mac OS X passwords