Information: Stolen Facebook Account

Situation
My Facebook account was taken over yesterday. I live in Germany at the moment, but a device called “123” logged in from the States and added all my friends to a group called “Football.Network”.
How it happened
I’m not 100% sure how it happened, yet, but my strongest lead right now is that it happened when I used the media playback application Boxee. For the first time I let the service post to my wall, at 20:31, and the unauthorized log in occurred at 22:52. Seems fishy to me.
Protect yourself
You can prevent something like this happening to you.
In Facebook, go to Account Settings -> Security -> Login Approvals. Tick the little checkbox so that you have to use your phone to confirm that you are you when you log in from a new device for the first time. This hasn’t worked with my network before, but it worked fine now, so this is definitely something you should do!