For those of you who are curious about seeing some of the hidden government-specific capacities of your Mac, run cac_setup from the terminal as root (preface it with sudo, in other words). Then user-switch over to the login window. You'll see some of the hidden bits where you can log in with a government access card reader. You can get back to being yourself through the "Other" user selection -- but you are first shown the standard DoD disclaimer that I see every day on Windows. Pretty neat.
When you're done, run cac_setup -off, again as root.
[robg adds: Wow, the DoD disclaimer is very thorough -- I was going to post a screenshot of it, too, but it's just too long!]

