Enable password for single-user mode (OS X)
Single-user mode by default is available on OS X without a password. This is not a desirable system behavior and to remedy this, all that is needed are a few simple commands. To enable a higher level of security we can set an “Open Firmware Password”.
On OS X 10.4.10, you need to use the updated version of the Open Firmware Password (v. 1.0.2) application from the software installation disc (located at /Applications/Utilities/ or at Apple-Support-Downloads). Then, just click the checkbox ‘Require password to change Open Firmware settings,’ set a password, and you’re good to go.

You are reading my mind. More on this later
Ok here’s why:
I was talking with Ian Gorrie about this blog post he did on USB Malware on OS X over a private email discussion.
I told him that he did good work on the post, and that people were talking about the Mac OS X NSA guides (I saw a bunch of talk around the blogs, I’m sure you can look it up).
Then I mentioned the single user mode problem for OS X and in turn, he mentioned setting a firmware password.
So, uncanny timing.