Your OS X Contacts database will also pull down your friends' names, snail-mail and e-mail addresses, phone numbers, birthdays and profile pictures, then keep them up to date whenever they change back on Facebook.
If it senses that you've fixed your gaze on a specific location for more than a few seconds, a nose-bridge mounted HD camera will take a 50 x 50 pixel snapshot and compare it to its image database -- much like Google Goggles.