How do I prevent Facebook on iOS 7 from accessing my location?
Indeed @cksum appears to be correct. I just tested this on my dev device that's never had Facebook installed. The app said that it knew my location and showed the blue location icon, but didn't show in the list of apps in Location Services.

I pressed 'send' and got the 'Facebook wants to use your location' message, which I accepted and now the app is in the list and allowed me to switch it off.

In conclusion, yes it appears that Facebook doesn't request the actual location data until you press send, at which point the app is added to the list in Settings.